first question...do you have a pop-up blocker or software that does that for you? If so, that could be causing it.
Another thing, do a search for IETie.dll if you have it, that's the culprit. I think it is contained in a registry key too so do a regedit and search for it. Check for unregmp2.exe
in processes under your task manager. Kill it and then do a search for it on your hard disk and remove it if it was running and is there.
Another thing to check...the hosts file. Go to c:\windows\system32\drivers\etc\hosts and see if the specific url has been blocked by something. More details on how to use hosts file: http://accs-net.com/hosts/how_to_use_hosts.html
Good luck!