A couple of times I've heard of someone having trouble registering a new login here. Almost always this is because the password does not meet the "must be at least 6 characters and contain letters and numbers" requirement. We are running the default phpBB requirements here so there's nothing special in use.
When registering, the standard phpBB screen applies. The black text about needing to use a real email address is not an error: it shows on all screens, even when the email address you're trying to register for is legit.
The red text is the error. So if it says something about a password, make sure your password meets the minimum requirements. When in doubt, throw in a special character such as a ! or #.
If you're still having trouble registering even with a good password, use the Contact Us link at the bottom of every page.