Unresolved kernel trap 0x600 - now can't start computer!

Question

Our Mac G4 (10.2.8, dual 1GHz, 1GB RAM) has been suffering from more and more frequent kernel panics and crashes (see my previous post: http://tinyurl.com/hxut9), and now seems to have died completely. This morning (it is left on all night, as it runs a kind of server) the screen was blank but the light was on, indicating it was running. No joy waking it up, so I held down the power button until it restarted. It then gave me the following message:
"Unresolved kernel trap (cpu 0): 0x600 - Alignment DAR = 0428005e2 PC=0x0008d3d8"
repeated all the way down the screen.
It now won't start up: it hangs on a screen with a blue background and white box with the progress bar stuck on "Waiting for network port mapper". All external hardware except screen and mouse are unplugged - usually, there's an external hard-drive and a scanner plugged in.
Can anyone help?
Some background: as I said in my previous post, we've had odd network issues with it recently, where it could access the internet, but the outside world couldn't access it (for the server, or for scheduled backups across the network). This was the case with the firewall on or off. An extended hardware test eventually (34th loop) gave the error code "modm /2 /8", which would suggest to me there was a problem with the MODEM, but we don't use that - only the network card. Disk Utility gave no errors.
Any help / advice would be much appreciated! Although we have a network backup of the data, we can't access it without that computer, and I need it urgently!
Thanks very much,
Alex
PS. Update: on the 4th go, it has now managed to restart! I am not optimistic about this lasting though, so would really like to resolve the issues...
Dual 1GHz G4   Mac OS X (10.2.x)   10.2.8, 1GB RAM
Dual 1GHz G4   Mac OS X (10.2.x)  
Dual 1GHz G4   Mac OS X (10.2.x)  

Answer 1

I've now managed to restart it again (it crashed after first restart, saying "FF:FF:FF:FF:FF:FF"), and have retrieved the panic log. Weirdly, the date for the last two entries seems to have been reset - the third most recent is Wed Jul 26 17:48:05 2006, but the last two are Thu Jan 1 01:33:03 1970 and Thu Jan 1 01:42:20 1970.
Anyway, the text of the latest one is:
Thu Jan 1 01:42:20 1970
Unresolved kernel trap(cpu 0): 0x200 - Machine check DAR=0xf0180a04 PC=0x0009269c
Latest crash info for cpu 0:
Exception state (sv=0x1B63C500)
PC=0x0009269C; MSR=0x40009030; DAR=0xF0180A04; DSISR=0x40000000; LR=0x1B657ADC; R1=0x16183D00; XCP=0x00000008 (0x200 - Machine check)
Backtrace:
0xF0180580 0x1B657ADC 0x1B65809C 0x1B658198 0x0020FF8C 0x00092950 0x00650073
Kernel loadable modules in backtrace (with dependencies):
com.sophos.sav.ic.kext(1.0.2)@0x1b655000
Proceeding back via exception chain:
Exception state (sv=0x1B63C500)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x1B603A00)
PC=0x9000550C; MSR=0x0200D030; DAR=0xF0180A04; DSISR=0x40000000; LR=0x9000C26C; R1=0xF0180480; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 6.8:
Wed Sep 10 15:20:55 PDT 2003; root:xnu/xnu-344.49.obj~2/RELEASE_PPC
panic(cpu 0): 0x200 - Machine check
Latest stack backtrace for cpu 0:
Backtrace:
0x000857F4 0x00085C24 0x000287B4 0x0008F6A8 0x000927B8
Proceeding back via exception chain:
Exception state (sv=0x1B63C500)
PC=0x0009269C; MSR=0x40009030; DAR=0xF0180A04; DSISR=0x40000000; LR=0x1B657ADC; R1=0x16183D00; XCP=0x00000008 (0x200 - Machine check)
Backtrace:
0xF0180580 0x1B657ADC 0x1B65809C 0x1B658198 0x0020FF8C 0x00092950 0x00650073
Kernel loadable modules in backtrace (with dependencies):
com.sophos.sav.ic.kext(1.0.2)@0x1b655000
Exception state (sv=0x1B603A00)
PC=0x9000550C; MSR=0x0200D030; DAR=0xF0180A04; DSISR=0x40000000; LR=0x9000C26C; R1=0xF0180480; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 6.8:
Wed Sep 10 15:20:55 PDT 2003; root:xnu/xnu-344.49.obj~2/RELEASE_PPC
If anyone can decipher that, please let me know! I can send previous panics if useful.
Alex
Dual 1GHz G4   Mac OS X (10.2.x)