[Lenny the Cup]

First of all; Don't select everything when you're not even looking for something specific. "SELECT `username`" is better.

Secondly, you aren't freeing the result - this will cause great problems after a couple of queries. Make sure to mysql_free_result(); after you have used all the information in every mysql_store_result();

And lastly, run mysql_debug(1); and look at the MySQL log and you shall find your answer.