EDIT: Sorry just read you have tried Firefox.......
Mmm - well I had a problem with IE6 back last year whereby it kept closing itself and all instances of IE6 down when you clicked a link on a page.
I tried uninstalls then reinstall's scoured the help pages, posted everywhere but nothing that matched my problem or that seemed to be able to fix it ! In the end I ditched IE6 (except for the automatic updates) and switched to Firefox.....
I realise you (like me) want to get IE6 working again, in the end I couldn't be bothered anymore, Microsoft even offered to charge me to fix it !!!
It may solve the problem for you if you use Firefox instead of IE6 to grab the download.
Regards