Robidoo:
I was having a similar problem, although mine came along with eventual crashes after awhile. Sometimes it would be an hour, sometimes 15 minutes. I also was having the issue with NVraidservice.exe crashing at startup, and I was getting the "Error loading operating system" error when I originally tried to install XP.
From what I understand, these problems are rather frequent, and their solutions may have been posted here before. If so I apologize, I simply do not have the time to comb through 70+ pages of material right now.
The fixes/workarounds I found are as follows:
--nvraidservice crashing: Was related to my Audigy 2 ZS Gamer, apparently Creative in their infinite programming wisdom include a utility in their drivers that looks for the extra front controls on the Platinum Pro, and this utility interferes with the nvidia raid drivers. Each company is pointing the finger at the other on this issue. If you are running RAID and do not let the service startup with windows, your HD WILL end up getting corrupted. You have to run services.msc and disable SBDrvDet in the startup tab. This solved the problem for me, and seems to be for everyone else as well.
--Random Lockups/Issues with performance/running programs:
The Nforce4 drivers interfere with SP2's automatic updates service. I have tried using both the new drivers as well as the ones found on the CD. Same issue. I found this out through XP's system log viewer (just started using it last week, already I don't know how I'd troubleshoot without it.)--everytime the wuauclt service was called up to check the microsoft site for updates, inevitably it was followed by an a paging file error on the system drive. I know the drive is good, worked fine in my last build. Unfortunately, the only workaround I've found right now is to completely disable the automatic update services in services.msc.
--"Error loading operating system" message:
For some reason, the BIOS (1003) ignores the boot order specified and tries to boot from the IDE drive immediately after the CD-ROM drive. I came across this problem installing XP; the files would copy over fine, but after the first reboot, I would get the error. I figured out that if you have a bootable CD in the drive but don't boot from it, for some reason the BIOS gives up at that point, or tries to hit the IDE device, and throws an error. The workaround I used was to simply disable the IDE channel in the BIOS I had the HD on, since my optical drive was on the other channel. Then I re-enabled it after installing XP. However, if you have to keep both channels enabled, you may be able to simply open the drive door containing XP immediately upon the reboot. Then reinsert after the computer boots from the RAID array.
Like I said, I still get the error to this day if I have a bootable CD in the drive but don't press a key to boot from it. I assume this will be fixed with a future BIOS update. Also, I concur that this board has issues similar to the NEO2 in regards to the DiamondMax 10 drives and resuming from standby. Hopefully this will be fixed soon also.
Sorry for the lengthy post, but I think this is a really awesome board but unfortunately because Asus wanted to capitalize on the early adopters and Christmas, we are dealing with issues like this. All this mobo needs is a little love!