I have seen a lot of posts in “alt.comp.periphs.mainboard.abit” where people are having problems getting the USB ports to work reliably. (mainly on KT7s)
I was having a similiar problem with my KA7-100, but only at bus speeds over 112Mhz.
It turned out to be my floppy drive that was causing the problems with the USB ports.
As soon as I disconnected the power from my floppy drive, all my USB problems went away.
The floppy drive is now getting its power from my secondary P/S (300w AT)–I use it to power my fans and my V5-5500.
Now my KA7-100 is working great at 119Mhz FSB with no problems whatsoever.
I thought you might want to post something about this since it may help some people get a bit more speed out of their motherboards as well as make them more stable.