Over the summer in 2006, I heavily upgraded my son's (mostly gaming) PC with a new Asus A8N-SLI motherboard (not the Deluxe model). Originally, it had an NVIDIA 6800 GT video card in it. It had been working for about six months with no problems. Over the holidays, I upgraded the video card to an EVGA 256-P2-N624-AR GeForce 7900GS 256MB 256-bit GDDR3 PCI Express x16 KO, which I bought from Newegg. I highly recommend the card for the price ($160 shipped at the time of this writing). After installing the new card, I ran the usual gaming and graphics benchmarks and was really happy with the nearly double performance.
Within the first day of life with the new graphics card, however, the Logitech USB optical Wheel Mouse (model # M-BD58) started freezing. Every five to ten minutes it would just stop working for about 20 seconds. Then it would start up again and run normally until the next freeze. I noticed this most when in Windows, but some games exhibited the same problem. In case you aren't aware, it's not a good idea for your mouse to periodically take a siesta in the middle of most first-person shooters. In fact, it's maddening. The mouse was a spare, and I was only using it because the mouse that goes with that system didn't make the trip home from college. I swapped out the mouse with a new wireless mouse from Kensington and the problem seemed to go away. I chalked it up to a bad mouse.
When my son returned to college and hooked up his Logitech MX-300 series mouse, the problem came back. Buying a new Logitech G5 gaming mouse didn't make the problem go away (but did score him a new gaming mouse). Doing some Goggle-research, I found the problem was not unusual, occurred mostly with Logitech mice (but not exclusively), and generally came down to some sort of IRQ sharing problem. Great. This is one of the reasons why I switched to Window XP way back when. I got so tired of resolving IRQ conflicts back in the day. I guess the problem never really went away; Windows XP just doesn't have it as often.
Sure enough, when we looked at the IRQ assignments, we found the USB controller and the video card (among others) sharing the same IRQ number. IRQ sharing is not unusual in Windows XP, and I've not really had a problem with it before. Back in the "old days," one could open the properties for a device, click on the Resources tab and change the IRQ setting. (Some details left out here - on purpose.) Windows XP doesn't have this capability it seems. I found one article in the Microsoft Knowledge Base that says basically just that. Moving cards around from one slot to another can change the assigned IRQs. That wouldn't help in our case because the only add-in card in this computer was the graphics card and the only choice is a PCI-e 16x graphics slot. (This motherboard has two slots to support SLI, but we didn't experiment with moving the card to the second slot - if that's even allowed with only one card.)
As the Microsoft article mentions, it is possible to change the IRQ assignments in the BIOS on many motherboards. I didn't really want to go to that extreme except as a last resort. My experience is fooling around with those causes more problems than it solves. (If you do go this route, make as few changes as possible.) Typically, to do this, you must first shut off ACPI (Advanced Configuration and Power Interface) support in the BIOS. Doing so almost guarantees that someone is going to be reinstalling Windows XP in the very near future. We found another more useful article, which talks about how one can clean up the devices in the device manager (especially USB devices). I had my son do that, and while it seemed to help (presumably by shifting some of the devices), it did not get rid of the problem completely.
What ultimately worked - and may only be useful to those of you with Asus A8N-SLI motherboards - is the latest 1604 Beta motherboard BIOS from Asus, which only became available on March 7, 2007. (There is also a beta version of the BIOS  available for A8N-SLI Deluxe owners.) The new beta BIOS release purportedly fixes sluggish performance issues with the Vista OS on this motherboard. However, Windows XP users are also reporting increased speed as well. For dealing with our specific problem - the mouse intermittently freezing, the new BIOS also moves IRQ assignments. The USB controller and video card are now on their own IRQs. So far, everything is working fine and the mouse hasn't frozen yet. We're crossing fingers (and nailing virtual bad-guys) here.