Usb external drive not working on vista

Good evening,

I have an extrenal usb hard drive which was working fine on my vista.
It suddenly stopped working on the same vista.
The hd works on other computer (xp).
Other usb devices work fine on my vista.
the hd is physically recognised but I cannot open it. In fact, once plugged in, windows explorer crashes... if I unplug it, vista saxs that the hd needs to be formated (The same hd works fine on another computer)
I deleted the infcache file but still have the same issue.
Any idea ?
thanks in advance,

Damien