Make sure the file muweb.dll is in your Windows/system32 folder then open a command line by going to Run... in the start menu and type in regsvr32 muweb.dll then click OK (note that there's a space between 2 and m).
If its not there then re-install Microsoft Update:
http://update.microso...pdate/v6/default.aspx
11:53 Fri 20th Aug 2010