Thunderbird weirdness

[hornet]

Anyone got any ideas what's going on here? I've got two Gmail accounts set up in Thunderbird, but since updating to 1.5.06, one of them is just refusing to work. I can log in ok via Gmail online, but when I run "get mail" in Thunderbird, I get a message that pop.gmail.com has refused the username/password, even though they're correct. I've checked all the account settings, reset passwords and even created a new profile, but no luck. I'm baffled!

This is on an XP Pro system, if that's of any relevance. I dual boot Linux, so suppose I should check to see if Kmail has similar problems.