Please provide relevant information, such as:
- The edition of Vista and what Service Packs have been applied
- The name of the installed antivirus/security suite and if a 3rd party firewall is being used
- How long this issue has been occurring
- Is the antivirus/security suite's subscription current; is it up to date in regards to the latest definitions;
when was the last time the system was scanned for the presence of malware.
In addition to the above information, please try another attempt at updating. If/when updating fails, close the Windows Update applet and then read this:
How to read the Windowsupdate.log file
Please post back with the requested information and copy&paste the last 50 or so lines of the WindowsUpdate.log into your reply, too.
What we're looking for is FATAL error codes, as explained in the KB article.
MowGreen MVP Data Center Management - Update Services Consumer Security