I didn't see the doc (yet, although I need to go get myself checked up for other reasons) but I'm now pretty sure that whatever it was, it wasn't RSI. My hands and wrists are now more or less fine, but last night, my back and knees were in a bit of pain. (They're OK now.) So I think it's just buggy joints. I need oiling. Mother suggested some glucosa-something or other which is apparently good for the job.