Logging In Using Firefox

Just a strange thing I have noticed. I use the password manager on Firefox 2 to enter passwords for many websites (not all of them). On the comodo forums when I come to log in, the firefox password manager asks for my master password. When I enter this it inputs my comodo password as expected. However the password manager then re-appears asking for my password again. If I do not enter it the second time firefox crashes half the time.

This is the only website where this happens - normally I just enter the master password, firefox puts my login and password in the relevent boxes and I press enter.

Strange, I wonder has anyone else found this - it must be something to do with this website as it does not occur for any other site.