Still happening on a fairly regular basis. Taken to copying any posts I'm composing for when everything grinds to a halt. The record so far for "Fetching preview" is over seven minutes, then it threw a strop and told me to try later.
Sometimes there seems to be a general slowing down even when there are only about a dozen members online. Then it either clears itself and works perfectly for a while or everything goes pear shaped, the forum page disappears and I'm told to try again later.
Thought the super duper new server was supposed to correct these problems.
Bob.