win2ksp4 - cannot stop/start services, install/uninstall software, use Internet Explorer

Hi,

Following a restart to attempt to clear an "offline" tape drive in Backup Exec I now find that if I try to install/uninstall/reinstall programs (I tried to uninstall Backup Exec) the installer doesn't respond, eventually timing out; Internet Explorer doesn't work, just a blank page (Firefox does work, and I can ping internal external sites and IP addresses) and if I try to stop or start any service via the services control panel that stops responding as well. Also terminal services clients get a non response if they try an "open with" context menu choice although that works fine via a LAN connection.

Help!!
(Thanks:)
.