Comment 2 for bug 194335

A quick fix for this is to do:

sudo modprobe i8k

I also believe you can add it to /etc/modules to avoid running it every time.

I just set up a new Xubuntu install on my notebook and noticed this same issue today, although I don't remember needing to add that module before on my Ubuntu setup (both installs are Gutsy) on this machine. Perhaps something just recently broke this.