I should add that in chasing down this bug I have tried all the IO schedulers available (noop deadline and cfq). Cfq is the one I'm now using to reproduce this. Also, I don't know if it makes a difference, but when the system first starts up it takes 20m to get from the login manager to having my web browsers restart and get all their pages from online. It might be because there is a lot of IO going on or it might be that there are several stalls in the scheduling; just not bad enough to cause a hung task problem like above.
