WSUS hangs during reboot

Hi

Some of our Win 2000 ang Win 2003 server wsus clients are not able to
schedule a needed reboot after installing patches. Windowsupdatelog shows :
AU invoking RebootSystem (OnRebootRetry)
WARNING: SUS Client is rebooting system.

Nothing in event logs...

These two lines loops until we do a "manual" restart...
When we do a system restart... Windows hangs on the shutdown screen and we
need to do a hard reset to solve the problem...

Any idea on this?

I´ve seen many other posts regarding this problem on other forums but no
solution...

Thanks!