Sorry about that everyone.
I've investigated the problem and I'm pretty sure it wasn't a problem with the source code or Bitcoin handling code. It seems to be something stupid I did with the database that let someone change their balance. This won't be a problem with the real version as the Bitcoin daemon as built-in checks against this kind of thing.
I've fixed the problem with blank usernames.
The site should also be back up.
I apologize for the fuck-ups; by software standards, we're still in the alpha stage of testing (hence why I released a demo first) and I'm happy we're catching the bugs now rather than later.
I've noticed that it looks like usernames are trimmed of spaces on the beginning and end of the string. This means that " user " would show up as "user" and " " would show up as "" which we already know is causing a problem with the table.
While I think this is a very nice setup (although in need of work) it is not ready for sale and you probably shouldn't take any orders yet.
I'll do my best to help out, though.
Edit - betting less than 0.000001 simply doesn't do anything.