Ok, this is partly UI trouble, but it's blocking my claim now, permanently.  Yes, I'm aware that MyBitcoin originally truncated the password, this is not the root cause of my problem at the moment.  Before the claim, when I re-installed 1Password after the Mac OS X Lion update, the default behavior is to auto submit the form after filling in the username and password.

Basically, I had 1Password fill in the claim form authentication.  But it automatically submitted the form right away.  Right before it submitted, it filled in my username as the claim address.  Now it says my balance is zero.