Well, looks like I'm getting the same errors in syslog, and was under K49 as well. I had gotten random reboots under K49, but that was wifi related. Once I removed the wifi AP for work (which is the only place it happened) it stopped doing it. But in those the opps clearly pointed at the wifi driver. This one is pointing at the kmem_cache_alloc call.

One thing I find odd though, why is fmtxd running on your system at all? On my N900, the only time that runs is when FM has been enabled and it's actively transmitting audio. By default it runs at start up but goes away on it's own after a short delay. So the fact that it was even running implies to me that something was trying to activate it?