I'm really not sure, I've never heard of that error before; but it looks to be a server configuration issue. Upon
Googling the error, I see a lot of references to pre-MySQL 4.1 style passwords (versus the hashing introduced in MySQL 4.1), but we're talking about a change from like 2003 (that looks like the release year of MySQL 4.1); so, unless you've been with your host for like ever (not sure why any current host would still be pushing pre-MySQL 4.1 passwords) I'm at a loss.
You could try changing this line in /libs/mysqli.inc.php
With
And UBB.threads should print the entirety of the error message, but I think that'll probably still be the one that the test script is displaying.
Could I convince you to mail me a copy of your config.inc.php file to james@virtualnightclub.net, I'd like to see if your configuration has any port definitions or if its configured to use persistent connections or something that may be off in the file.