Hello! I've been running 5.4.1.1 without any problems. A couple of days ago I discovered that new users are having trouble registering. I have both the captcha and validation email enabled. New users just keep getting bounced back to the registration page after entering the captcha, as though they've typed it wrong. But they haven't.

One possible clue: I was able to repro this when I tried to create a new account, but it suddenly worked fine when I changed my email address. This made me wonder if the registration system gets confused if the email address isn't unique. But I don't think this explains the problem for other users.

Has anybody else seen this? Any ideas on how to fix? Thanks in advance!