I have added some info that is generated once the page has appeared that will hopefully help track down the problem. Your help is required.
Once the page has appeared after an unacceptable wait, scroll to the bottom of the page and send me a pm with the information that appears there.
This should start me off looking for a fix.
Also while you are waiting you could try looking at the main site in a different tab or browser just to see if the the site is stalled or if it is just the forum. If it's just the forum that is having problems then it might be time for upgrading.