Vista update hangs

Problem 1: A month old machine running Vista 64 home. All fine until
last few days. Now Windows Update opens a box with the heading
"Control Panel - WIndows Update" and it hangs with a spinning disc
(hourglass). I can only then kill it with Task manager. This happens
whether I start from control panel or from the start menu.

Problem 2: A year old Dell laptop running Vista 32 home. Win Update
worked fine until I installed Office 2007 this morning and I now have
the same problem as above. (Problem 1 machine also has Office 2007).

No error codes - just the hour glass and utterly unresponsive.

Any ideas please?