Ok, definitely MySQL related. First question would be if you are on your own server or if this is a shared server. If it's shared your somewhat at the mercy of your host. It could be that they just have too many customers utilizing the MySQL server so it's slow.
I just visited your forum and it's pretty small, so really there is no reason for it to be slow at all. If this is your own server then even the default MySQL config with little memory and CPU should be running that just fine.
So, I'm going to guess your on a shared host and you might consider inquiring about the number of customers utilizing the MySQL server. If they can move you to one that isn't overloaded, or if you need to go to a new plan/provider.
If this is your own server, then we'd need some info on the server specs.
