Comment 27 for bug 749871

As an additional data point:

My x120e used to crash when I used the standard realtex drivers in Natty kernels (and also IIRC, with the standard Oneiric kernels). After upgrading the kernel (to 3.0 if I remember correctly) and switching to the driver from the Realtek web site (0005.1230.2011)--I believe both upgrades were required--I was able to eliminate the system crashing. I am now running 3.2.0-15.24 kernel with the driver's from the Realtek web site, and my machine hasn't crashed for some time.

Unfortunately, however, the machine still drops the wireless connections frequently on certain wireless networks (usually ones with multiple access points and enterprise level security).