Hmmm.... there is no cookie prefix in phpbb3. I tried changing #215 cookie prefix to phpbb3 but that didn't fix it. I changed it to my cookie name, that didn't help. I also "blanked" that field out. Still no luck.
If you need a screenshot let me know. The problems are here: http://www.obd-codes.com/reviews/
Edit: I also tried clearing my cookies and logging in again. It seems to "login successful" but my cookie info is displayed above all content and I cannot access Admin / Upload. It just says "Home / Search / Member List / Register / Login".