USB 2 problem

[Ness_du_Frat]

I have a strange problem... All my usb ports on my computer are usb2, I have Win XP SP2, so no problem on this side.
However, the computer doesn't recognize those ports as usb2, and thinks they are usb1 only.
I have a DVD burner, which is once in a while recognized as plugged on an usb2 port (and everything goes fine), and the rest of the time, the computer thinks the port is usb1, and the burner takes something like 3 hours to burn a DVD on 16x speed...

What I've been trying so far :
-updating the usb2 driver
-buying a new usb2 cable
-switching from a port to another
-uninstalling the usb2 driver and reinstalling it

I don't know what else I can do... any ideas ?

[Ness_du_Frat]

Ok, it still doesn't work.
I've tried :
-booting in safe mode after uninstalling all the usb in the peripheric thingie (gestionnaire de périphériques, in FR). Uninstalling them again. Booting in normal mode. (they all got recognized at once by Win XP)
-using the default driver from Windows
-flashing the BIOS

Nothing works...

Any other idea ? I think I've done it all, by now. Or is there something remaining ?