Registering for a Stack Exchange OpenID is a huge pain; it took me 20-30 attempts. I ran into two problems you might want to look into:
First, there's no indication of password policies:
- Password length
- Character repetition
- Mixture of uppercase, lowercase, numerals and, quote, "special characters"
I tried a bunch of passwords before I hit on one that worked.
Second, 50% of the time I can't make out what the CAPTCHA displays, so I kept getting it wrong