I've taken the difficult decision to reset everybody's passwords this morning (I did tell you the site was in beta, didn't I?) in order to implement a higher level of encryption in the database.
It won't effect you until your session cookies run out, but essentially you will have to reset your password via the "forgotten password" link next time you login, after which you will be free to change your password back to whatever you want in the account settings page.
Apologies for causing so much hassle. This was just one of those times where taking the hit now means we don't have to worry about it again.
Thanks for sticking with the site, and keep the ideas coming!