It works with some of the machines I use and not others.
Desktop at home, FF3.5.2, Win2K, only works in Private mode, worked fine until about 10 days ago.
Laptop at home, FF3.5.2, Win 2K, works fine all the time.
Desktop at work, FF3.0.14, Win 2K, works fine all the time
Other desktop at work, FF 3.5.3, XP SP2, only works in private mode.
To Shane 8, this is a personal account I am trying to access, not a company one. We use Natwest Bankline for our work banking and that works on all 4 of my machines, at home and work.
All the machines have the same add-ins, NoScript, ABP, FlashBlock, ShowIP and DownThemAll
I had the "we only support Internet Explorer" from their help desk as well