At the moment some people my be seeing that. Whats actually happening is there appears to be a rogue query or table item within the database that whenever it is being run, locks up other queries behind it until it has finished doing whatever it is.
At that point all the other backed up queries (like people wanting to post, or read a page) get run in the blink of an eye.
Currently trying to find what it is thats causing this, as it has been fine for quite some time, and then suddenly started misbehaving.
To be fair the way we have modified phpbb3 from its original out of the box state, its a wonder its not happened sooner. We will find it and fix it though.
A move to a different platform more in keeping with the size of this board has not been ruled out - but we know how people like the look and feel of this site, so we arent rushing into that option.