I had to register after happening upon this thread.
I have been having the random freezing problem with the ep-9npa+ ultra board for some time now. Of interest, I have owned the board since its release (about a year now?), and the freezes did not exist for many months. When they did start to occur, they were when I was using a single core 3000+ processor. I routinely keep up with the latest drivers and BIOS revisions (when I think that there is a meaningful fix). No new hardware was added at the time the freezes started - I had USB 2.0 enabled on the motherboard and several USB 2.0 devices including thumb drives, printer and scanner but no external hard drive. Furthermore, the freezes were indeed random, independent of usb device usage or anything else I could nail down. Every piece of hardware in my machine (except the MB) has been replaced and the OS reinstalled multiple times but the problems have persisted - I most recently replaced my power supply thinking that was the problem. Again, of note, the freezes continued after a processor upgrade to the x2 3800+. In addition, I have no heat issues (CPU temps 44 deg max and chipset temps around 30 deg)
After reading this thread I disabled SMART monitoring which did not work. Flashed to the most recent BIOS (now the 12/21 release I believe?) which also didn't work. Installed the dual core hotfix from Microsoft - again, a no go. Subsequently, I installed a Belkin usb 2.0 PCI adapter and disabled usb 2.0 functionality in the BIOS (it is now limited to 1.1). All usb 2.0 devices are now connected to the Belkin card. I have had no freezes in 36 hours now, and I would typically have an event in this time period before. Furthermore, the computer now enters and resumes from standby more reliably than before.
All this is to say that I don't believe this problem is an x2 issue at all. It is either the result of the random failure of a hardware item on the board (capacitor?) or it is a driver problem.
In this forum:
http://forums.nvidia.com/lofiversion/index.php?t8928.html, several members report similar problems on an Asus board using any Forceware drivers more recent than 78.01. My personal feeling is that this is related to the Chipset drivers and usb 2.0 implementation, but I have not reverted to the original driver version to test it out (currently using 6.70).
Anyway, just my two cents on this topic. I am 50/50 on discouraging someone from buying this board based upon this issue alone, particularly if it can be easily remedied using an add-on USB adapter. It might be worth considering Epox's newest board based upon the nforce4 ultra chipset (the ep-9npa3ultra), available from the Egg here:
http://www.newegg.com/Product/Product.asp?Item=N82E16813123258. Other than a change in board layout, I don't see any major differences from the ep-9npa+ ultra.
Happy new year, and thanks to all for the information in this thread. I will post again if I have another freeze.