Hahaha guess what? I accidentally deleted my own topic thread when trying to work it out myself! Luckily it was only a fledgling and hadn't gathered much momentum as yet, and I had the OP saved on my desktop. Not ideal, but problem solved lol.
In answer to your question, I can answer other topics in that forum without a hitch, though I did also have the same issue when PM'ing another user. But that seems to have been a one-off. I don't recall seeing any particular error code numerically, other than a page with the title "Internal Server Error" with some text I can't remember underneath.
Either way, due to my idiocy in deleting my own thread it's no longer a problem for me. For now... Happy new year!