have you carried out a virus scan with an updated AV?
did you uninstall the old drivers before installing the new ones?
in control panel/system/advanced/start up and recovery/settings untick the automatically restart box.you will now get an error instead of a restart.(make a note of the error)
try click here it is very good and will remove all traces of old drivers safely.then you can install the latest 3.6 cats again.(run it in safe mode)