#2 why endless re-login requests with firefox?

[HoTP]

I'm been using Firefox 1.5.x.x for some time and after
logging into https://sourceforge.net, sourceforge
keeps demanding I re-login every time I try to access
or commit an administrative function for our project.

I had to actually go back to using Internet Explorer
just to do minor admin' work on our project.

Can you please suggest a reason for this and how I
might fix it so I can use Firefox again? Thanks.