Why did this solve my USB mouse problem?

Hi

In the BIOS of the Gigabyte GA-7VAX motherboard there is an option to enable/disable USB mouse support. Since I use a Microsoft IntelliMouse Optical USB mouse, obviously (or so I first thought), I had to enable it. For three months everything seemed fine until recently when my mouse was, occasionally, no longer detected during POST and the cursor started to move erratically before it stopped responding. Not even formatting, reinstalling Windows and drivers, etc. helped.

I returned my PC to the retailer from whom I bought it, where I was told that this is a “common” problem with the motherboard/VIA chipset and that I must disable USB mouse support in the BIOS as my operating system (Windows 98SE) has built-in drivers for this and somehow “conflicts” with the BIOS.
Since I followed the advice and disabled USB mouse support I have not encountered any further problems except that my mouse no longer works in Safe Mode.

Can anybody explain to me why this solution worked? Why only after three months have I encountered any problems? And how I can get my mouse to work in Safe Mode again?

Cheers

SUNDEVIL

GA-7VAX (F10/Hyp. 4.46v),XP2000+,512 MB Nanya DDR333,80 GB IBM,1.44 MB TEAC,50x ASUS,Leadtek Geforce 4 TI4200 128 MB AGP 8x (43.45),SB Live! 4.1,Accton EN1207D 10/100,Windows 98SE (DirectX 9.0a).