Hi Laurence, are you using Windows XP as the issue usually occur on Windows XP instead of Windows Vista. If this is the case, I suggest you check the solution in KB890737:
http://support.microsoft.com/kb/890737
You can also post it to Windows XP forum:
http://forums.microsoft.com/TechNet/default.aspx?ForumGroupID=561&SiteID=17
If you are using Windows Vista, I suggest you first try System Restore. If the issue still occurs, please creating a new user account and see the result.