Comment 42 for bug 157777

i had this on an Amilo A1667G laptop with amd turion, disabling the dynamic frequency scaling solved that problem.

so please test disabling the default frequency scaling tool: powernowd

you can do this for your current session by:

sudo /etc/init.d/powernowd stop

when this solves your hard freezes, better report to the more specific bug report https://bugs.launchpad.net/ubuntu/+source/linux-restricted-modules-2.6.20/+bug/109643

you can also try to disabling powernowd completely on your system by just removing the package through apt-get or synaptic until there is a fix, like i did it.