Thanks to Mark, we now have a reason for the site crashes we've been having recently:
Our SMF Messages table, essential to the smooth running of the forum, is dangerously over full. The server cannot handle querying all that data, and unless something is done we're going to keep crashing.
We have 2 possible solutions at this time.
#1. Either we can either move to a new, better server (expensive) and appoint a full time database-handler (big job not understatement).
#2. Or we can delete 1/3rd of all posts from the forums and begin a frequent cull in future.
Option one will only be a stop-gap measure if the table keeps growing, and AIFAIK we have neither the money nor a person with enough time or experience on their hands.
That Leaves option 2, which if enacted would mean losing 30,000 posts. As I'm loath to delete old modding threads without a thorough checking, that probably means almost everything in the archive, chat and freepost. Future culls will be taken from suggestions and may come from anywhere on the site.
This thread is a chance to come up with an option three. Failing that, I will now take suggestions on which threads to save.