I recently had a problem with my installation of Office 2003 where when trying to Update via the MS site the progress bar would reach 40% and then drop out with an unable to continue message.
I tried various fixes for this from search results with no success, then emailed Microsoft support, they responded within two days with one suggestion for a reinstall using a clean up utility - this failed to clear the problem. They then responded again in a day and a half with a new procedure involving removing all traces of office from the registry and a re-install, this fixed the fault. I consider this to be an impressive time scale considering the size of MS and the amount of software out there.
If anyone has this problem I can post the fix or email it to them, although it does involve searching and deleting from the registry.