Go back to Windows Update, but then select View update history. (When you first get to website for Microsoft Update-Windows Update, look at left-hand column, under Options. Press "Review your update history".)
If this is on V6 of Windows Update, you should be able to click on that error note, and see some info.
Look at your log file for Windows Update. There may be another exception noted that preceded this one.
If you cannot find it, post an *extract* from the log, but only for the very last date.
Use Wordpad and open & look at the Windows Update log file
C:\WINNT\WindowsUpdate.log
Scroll down all the way. Get / copy / paste (ideally, put into a file & attach in reply back here) the set of lines for (today's ) the last session.