Some malware will block the site. I see this question a lot and have downloaded the file from Microsoft and uploaded it to my webserver as a quick fix. Here is the link:

http://www.geekinesshardcore.com/Fil...Converters.exe

Read the following link... it may shed some light on you situation.

http://www.malwareremoval.com/forum/...p?f=11&t=44519