As mentioned recently, I had an issue with the Dejal server that prevented people from registering for accounts on the site, and thus new people were unable to create forum posts.
After addressing this issue, I was (unsurprisingly) buried under an avalanche of spammer account registrations and spam posts, some of which appeared on the site, and were manually deleted by me as soon as Simon told me they were there, and some were automatically unpublished.
For a day or two, I tried requiring approval when registering accounts, but that didn't really work, as I couldn't tell who was a legitimate customer, and who was a spammer, until they actually post something.
So I am now trying another option: forum post moderation. Now, every new forum post will go into a moderation queue, requiring my manual approval to be seen publicly. This isn't ideal, since that means others couldn't help the author before I see it, but I usually see posts very quickly (again, thanks to Simon), and reply promptly. So it shouldn't have any real effect.
We'll see how this goes. Hopefully this step should prevent any more spam. If it works out, I could extend things further to "white-list" people who have posted legitimate topics, so their subsequent posts bypass the queue.