I have just tried to log in as Administrator on one of my PCs to do some routine housekeeping, only to find that it does not fully load. All the icons display (except the MS Office shortcut bar), but nothing happens when I double-click them. Also the Taskbar does not display, and I cannot bring up the Start menu with the Windows key. Ctrl+Alt+Del brings up the usual window of Log Off, Shut Down, Task Manager, etc - but none of the buttons responds: the only way out is to reset. Yet all the various user logins/desktops work normally.

Hope someone can come up with an answer - I need admin access for Windows updates, etc.

XP Pro, SP3, fully updated.