Error/moodle/cmunknown

I got here when trying to save a random matching question after changing the number of questions from 2 to 5. The error text was something like "the course module was unknown" and there was i link here. But I recognize that there has been some mention in the forums of this cmunknown error. I'm using Moodle 1.8.3 on a linux server viewing with Firefox on an XP computer.

See you!