Just bought the game, got the email and created a strong password. The password was 23 characters long and contained parentheses and a semicolon.
When I try to login with this password, it says my username/password is incorrect.
I suspect the semicolon (or length) of the password caused a problem behind the scenes that wasn't caught on the password set page.
I reset the password to something shorter with only alphanumeric characters and that worked, but wanted to tell you about the bug. If the semicolon was truly the issue, this could be an SQL injection vulnerability. Hope Bobby Tables doesn't sign up
Just to head off any PEBKAC concerns: I did the same thing I always do for passwords, which is type the full password out in notepad and copy/paste as needed. I copied the full password once and had it on my clipboard while pasting into the "set password" field, the "confirm password" field and then the login page. I checked my email address repeatedly as well.