Mac laptop issue
I appear to have a serious problem with my laptop, and I'm wondering if any of the technically savvy folks I know have any advice on what to do about it. Since I'm guessing that most people aren't particularly interested in reading about problems with my four(?) year old Powerbook (possibly related to overheating), I'll hide most of this behind a cut. (Whether you have technical advice or not, I'd also welcome any thoughts or advice on whether the tech support people in my local Apple Store are a reasonable option in a situation like this.)
The timing on this is particularly poor, since I'm giving the physics colloquium at Mudd on Tuesday. (My presentation is backed up in several places, but I'd planned on updating it a bit before then. In any case, I should start looking for a computer to borrow to give it with. Hmm... maybe the other folks in my office would have one to lend for the day.)
The short-short version is that in the past couple of days my G4 Powerbook (15" 1.25GHz, running the latest OS X 10.5.x) has started crashing on me. I suspect that overheating may be the cause: if I start it up after leaving it alone for an hour or so, everything goes fine for a while, but then at some point the system just freezes (details in a moment). If I attempt to reboot immediately, the computer usually makes at least some progress (perhaps even getting as far as letting me log in or even open a Terminal window), but pretty quickly crashes again. Further immediate attempts to reboot often don't progress beyond the startup sound: the screen remains blank, and the system may in fact shut itself back down. If I leave the computer alone for another hour or so, it boots up fine again.
I'll give more details below, but I'll state my basic question right away: what are my options here? I could imagine this being as simple(?) as a balky processor fan or as nasty as a circuit on the motherboard that's become permanently hyper-sensitive to heat (or just to being used). Are there /any/ possible causes for these symptoms that I could identify and fix myself? How effective would it be to take the computer to the nearest Apple Store for help? Do any of you have experience with Apple tech support people that would help me know how to make the most of a visit there (or even what level of competence and/or timely service to expect)? What are the odds that I'll be able to use my own laptop to give the physics colloquium at Mudd on Tuesday?
On to some details:
I have booted successfully to various install and recovery DVDs (as long as I've left the computer alone for a while beforehand). Disk Utility insists that my hard drive is fine. The free "memtest" utility shows no RAM errors (I ran it after booting to single-user mode). I ran Apple's DVD-based hardware tests, which said that everything was fine until the system froze in the middle of the video RAM test. I'm hesitant to blame the video RAM, however: that was the last test to run, and the laptop had gotten fairly warm by then. (As usual, attempting to immediately re-boot and run the hardware tests again led to an early freeze: the system got stuck while I was trying to select the hardware test option at boot time.)
When the system does freeze (after a normal boot), the symptoms vary. On a couple of occasions, everything on the screen except the mouse pointer simply stopped responding in any way. (I could move the mouse pointer to my heart's content, but clicking on things accomplished nothing.) I've also seen the dark grey "You need to reboot your computer" rectangle pop up a couple of times (which I believe means "kernel panic"), and I actually saw plain UNIX-ish text print over the desktop once with a much less user-friendly kernel panic report. (One of those messages also showed up on boot once.)
I could make some sort of comprehensive list of everything I've observed and tried, but I've probably already given far more information than necessary. If there's more that you'd like to know, just ask. And thanks in advance for any advice you might have, even if it's just "Pray to the deity of your choice" or "Check your bank account balance."
The timing on this is particularly poor, since I'm giving the physics colloquium at Mudd on Tuesday. (My presentation is backed up in several places, but I'd planned on updating it a bit before then. In any case, I should start looking for a computer to borrow to give it with. Hmm... maybe the other folks in my office would have one to lend for the day.)
The short-short version is that in the past couple of days my G4 Powerbook (15" 1.25GHz, running the latest OS X 10.5.x) has started crashing on me. I suspect that overheating may be the cause: if I start it up after leaving it alone for an hour or so, everything goes fine for a while, but then at some point the system just freezes (details in a moment). If I attempt to reboot immediately, the computer usually makes at least some progress (perhaps even getting as far as letting me log in or even open a Terminal window), but pretty quickly crashes again. Further immediate attempts to reboot often don't progress beyond the startup sound: the screen remains blank, and the system may in fact shut itself back down. If I leave the computer alone for another hour or so, it boots up fine again.
I'll give more details below, but I'll state my basic question right away: what are my options here? I could imagine this being as simple(?) as a balky processor fan or as nasty as a circuit on the motherboard that's become permanently hyper-sensitive to heat (or just to being used). Are there /any/ possible causes for these symptoms that I could identify and fix myself? How effective would it be to take the computer to the nearest Apple Store for help? Do any of you have experience with Apple tech support people that would help me know how to make the most of a visit there (or even what level of competence and/or timely service to expect)? What are the odds that I'll be able to use my own laptop to give the physics colloquium at Mudd on Tuesday?
On to some details:
I have booted successfully to various install and recovery DVDs (as long as I've left the computer alone for a while beforehand). Disk Utility insists that my hard drive is fine. The free "memtest" utility shows no RAM errors (I ran it after booting to single-user mode). I ran Apple's DVD-based hardware tests, which said that everything was fine until the system froze in the middle of the video RAM test. I'm hesitant to blame the video RAM, however: that was the last test to run, and the laptop had gotten fairly warm by then. (As usual, attempting to immediately re-boot and run the hardware tests again led to an early freeze: the system got stuck while I was trying to select the hardware test option at boot time.)
When the system does freeze (after a normal boot), the symptoms vary. On a couple of occasions, everything on the screen except the mouse pointer simply stopped responding in any way. (I could move the mouse pointer to my heart's content, but clicking on things accomplished nothing.) I've also seen the dark grey "You need to reboot your computer" rectangle pop up a couple of times (which I believe means "kernel panic"), and I actually saw plain UNIX-ish text print over the desktop once with a much less user-friendly kernel panic report. (One of those messages also showed up on boot once.)
I could make some sort of comprehensive list of everything I've observed and tried, but I've probably already given far more information than necessary. If there's more that you'd like to know, just ask. And thanks in advance for any advice you might have, even if it's just "Pray to the deity of your choice" or "Check your bank account balance."