But I thought that the problem comes from the PCI Bus being denied so wouldn't that be a hardware problem and necessarily software?
Nope. Even the Creative Titanium, which uses the PCI-E bus, has this problem from time to time. Kinda rules out the PCI bus as a culprit. Likewise, a LOT of people claim the Daniel_K and PAX drivers help them with the issue.
That being said, I simply recommend either ASUS and HT Omega, avoiding the X-fi chipset entirely.