Strange Error Message after prolonged inactivity

Question

I have a PowerMac G5 (1.8 Ghz, 900mhz bus speed, with 1.5 GB of RAM installed.
If this machine is left running overnight, wheth it is asleep or not, by the next morning, the following error appears on the screen:
obj~1/RELEASE_PPC
MEMORY ACCESS EXCEPTION (1,0,0)
Ethernet MAC Address: xxxxx
IP address: xx.xx.xx.xx
Waiting for remote debugger connection.
It appears to be a kernel panic of some kind; my theory based on the error message is that there is a memory leak on one of the memory modules. I have taken the following troubelshooting steps:
-Run ASD for PowerMac G5 and it passed all tests.
-Run Techtool Pro hardware tests, and it passed all tests.
-Searched for applicable firmware updates, and when run, I get a message that the firmware is up to date.
-Reset SMU.
I have a second G5 that is starting to do the same thing. However, the one in question is doing this frequently, as in every night.

Answer 1

Actually, I believe I've got it troubelshot down to a software and not a hardware issue. I checked the kernell panic log and saw that Virex was consistently causing kernel panics before 8:00 AM. I removed Virex, and everything is fine.
I sort of inherited support on these G5's, so I am uncertain about the memory in them. I have not yet had reason to crack the cases on them. I want to eliminate software first.