Try deleting cookies and cache:

1. Tools| Clear recent history

2. Time range to clear: Everything

3. If it isn't already selected, select Cookies and Cache

4. Clear now

Does the page work in Diagnose Firefox issues using Troubleshoot Mode?

I had problems with 4shared pages not loading at all, and Megaupload pages telling me that there was an "unknown error" when clicking the downloading link, and clearing the cookies fixed both problems