OK, sorry - I obviously wasn't concentrating ...
Yes, generally modules would/should be compiled against the appropriate kernel. There are all sorts of potential (dependency) issues; at compile- as well as run-time. Don't see it often, but possible.
You can force load the module (might work ok), or you could try retro-fitting the patch to the old kernel. Ugly.
Let me think some more (this post to put me back on the subscribed list).