Simply put, the way that MySQL stores user passwords changed in version 4.0; you have a couple of choices:
1. Reset your password, all is well.
2. Set MySQL to run passwords how it used to; its again fairly easy and an edit in the my.cnf, although I'm not sure of the exact steps, just google it for a full answer.
As for the PHP error, I'm not entirely sure off hand, but I'm guessing its due to the double // before tbopen.tmpl
