The Irish Mitsubishi FTO Owners Club

I've tried this both at home and in work so it's not PC specific but I can't log in here using the new Firefox 3.0.1.
If I enter username and password it just goes straight back to the main forum page and I'm not logged in.

No problem on either PC using IE7 / XP.

Any ideas?

I'm using the same version of firefox, no problems logging in though.

It's wierd - I've tried the usual suspects, clearing cache & cookies - no better. There's different antivirus systems between work and home so I'm guessing it's not that.