Kernal panic fixed by hardware change??

Question

Hello,
I have a G4 that I've upgraded quite a bit* and during the last month it has been randomly** suffering from kernel panics, sometimes when I'm using it, sometimes when it's left on its own. When I reboot (as the screen instructs me), the computer gets as far as the grey apple logo (but no spinning loader) and goes into kernel panic again.
Previously I had had to leave the machine for several hours before I could successfully reboot again. Recently, however, I've discovered that if I say unplug the DVD drive or swap a stick of RAM the machine will reboot successfully immediately.
So I'm wondering why, when I alter the hardware attached, should the machine boot up immediately as opposed to me having to leave it for several hours if I don't? Could this be a screwed motherboard (pls say no)? What goes on during the early stages of boot that would in effect reset the system preventing the kernel panic?
I've reinstalled the OS and have recently started to check the hardware, which I will continue to do. I write now because I believe if I can find out why hardware changes temporarily fix it I should arrive at answer sooner.
NOTES
* - Upgraded 2 months ago with Sonnet Encore 1.6GHz cpu and ATI 9000 graphics card. Machine run for about a month with absolutely no problem. Sonnet say its not the CPU.
** - Can be anything from 2 days to a week between crashes.

Answer 1

I have a similar problem with kernel panics and freezes but the computer will restart again afterwards and I don't have to shift my hardware around to get it to do so. However it has stopped chiming at start-up which I know is bad. It is a little more stable if I stay in the log in screen and access from my other computer on the network but it will freeze even then at times. The error log for my panics is:
panic(cpu 0 caller 0x000A8A00): Uncorrectable machine check: pc = 0000000098DE2660, msr = 000000004000F030, dsisr = 42000000, dar = 00000000E02FE000
AsyncSrc = 0000000000000000, CoreFIR = 0000000000000000
L2FIR = 0000000000000000, BusFir = 0000000000000000
Latest stack backtrace for cpu 0:
Backtrace:
0x000952D8 0x000957F0 0x00026898 0x000A8A00 0x000A8148 0x000AB980
Proceeding back via exception chain:
Exception state (sv=0x38165780)
PC=0x98DE2660; MSR=0x4000F030; DAR=0xE02FE000; DSISR=0x42000000; LR=0x00000058; R1=0xF0305840; XCP=0x00000008 (0x200 - Machine check)
Kernel version:
Darwin Kernel Version 8.9.0: Thu Feb 22 20:54:07 PST 2007; root:xnu-792.17.14~1/RELEASE_PPCModel: PowerMac3,5, BootROM 4.3.3f2, 2 processors, PowerPC G4 (2.1), 1 GHz, 1.5 GB
Graphics: NVIDIA GeForce4 MX, GeForce4 MX, AGP, 64 MB
Memory Module: DIMM0/J21, 512 MB, SDRAM, PC133-333
Memory Module: DIMM1/J22, 512 MB, SDRAM, PC133-322
Memory Module: DIMM2/J23, 512 MB, SDRAM, PC133-333
Modem: Spring, UCJ, V.90, 7.0F, APPLE VERSION 0007, 7/31/2000
Network Service: Built-in Ethernet, Ethernet, en0
PCI Card: usb, usb, SLOT-3
PCI Card: usb, usb, SLOT-3
PCI Card: pci1735,e0, SLOT-3
PCI Card: pci9004,7850, sppciscsibus, SLOT-4
Parallel ATA Device: ST380021A, 74.53 GB
Parallel ATA Device: ST3120026A, 111.79 GB
Parallel ATA Device: PIONEER DVD-RW DVR-104, 2.64 GB
USB Device: Hub, Up to 480 Mb/sec, 500 mA
USB Device: C-Media USB Headphone Set, Up to 12 Mb/sec, 500 mA
USB Device: HP ScanJet 6300C, Hewlett-Packard, Up to 12 Mb/sec, 500 mA
USB Device: Hub in Apple USB Keyboard, Alps Electric, Up to 12 Mb/sec, 500 mA
USB Device: Nostromo SpeedPad2, Honey Bee, Up to 1.5 Mb/sec, 100 mA
USB Device: Microsoft Trackball Explorer®, Microsoft, Up to 1.5 Mb/sec, 100 mA
USB Device: Apple USB Keyboard, Alps Electric, Up to 1.5 Mb/sec, 250 mA
USB Device: USB Device, Up to 1.5 Mb/sec, 500 mA
USB Device: iMic USB audio system, Griffin Technology, Inc, Up to 12 Mb/sec, 500 mA
I would really appreciate some ideas on how to resolve this. I will look over that Resolving Kernel Panics article as well.
Thanks