FC4 x86_64 system crashes every 7 days

[Jurgen Kramer]

It seems that my server always crashes after 7 days and some odd hours.
When I find it crashed the harddisk light is always on continuously. The
problem is that this system does not have a monitor on it so I cannot
see what the cause of is.

Any ideas how to determine what the problem is? Dmesg does not reveal
any clues. 

System specs:
Asus A8N-E running FC4 x86_64 (fully updated)
1x SATA disk for system and swap
2x SATA in software RAID-1

Jurgen