My problem was that my USB intellimouse was working but wheel did not generate any event (checked with xev), so, i had no scrolling in kde apps.

My XFConfig-4 file was configured correctly, but i had no clue. After googling quite a lot (without wheel-scrolling web pages) and finding out many people had the same problem but no solution, i considered coming back to 2.4.24

Then i downloaded usbutils and ran lsusb to find out ... nothing !

The solution is there, and i'm a noOb i had only to load the module uhci-hcd which wasn't needed in 2.4.24 (it didn't even exist i guess). No it works great with scrolling etc...

Actually my mouse was used as a PS2 one but via the usb port quite confusing...

My post is only intended to help others who would have the same problem. First step is to get usbutils and check that something is seen on your usb port