Update:I've installed an alpha build of Intrepid Ibex, the next Ubuntu version after Hardy Heron, on a separate partition and I haven't had any weird freezes. I haven't given it as rigorous a test as I probably should, but it appears to be okay. This leads me to believe the freezes I was experiencing were caused by the kernel version that shipped with Hardy (2.6.24), which is known to be buggy and unstable on many systems. Intrepid, on the other hand, uses 2.6.27, which seems to be rock-solid. I believe you can manually backport the 2.6.27 kernel to Hardy using Prevu, an automated backporting...
