I was thinking that there could have been some network congestion when he wrote the config file at one point and something could be hosed; hence asking to validate the data in the config file...
Though it seems complete enough to attempt a login with a user/pass of some sort, hence asking to check the u/p set in the ubb against phpmyadmin or another mysql tool to ensure it's allowing login from this combination.
It's possible if you have some sort of limits setup with the sql username to thwart abuse that the username got suspended in the system for going over quota; the persistent mysql crap takes a lot of resources and can hit a db in ways you don't want; hence why it's not recommended to use unless you understand what you're doing 110% (I wouldn't even bother with it).
I think we should nuke the option from the CP completely, and require users to manually turn it on in the config file should they understand how to use it and want to use the feature without accidental hosing their server lol... It'd be like classic's hidden ticks in the lib files way back when...
