Comment 76 for bug 574910

Rod, Alexandre, Matthew: your problem maybe at least partially related to Bug #585092, which is actually a little more generic than just umount.

Chris, something certainly isn't right with your system, but the fix from this bug isn't going to help you as it only applied to the -ec2 kernel. Outside of EC2 the high load average for an idle machine hasn't been generally reported as a problem. Can you please open a new bug so that we can gather more information and start tracking this problem down. From a terminal do
  ubuntu-bug linux

and follow the prompts. This will gather information from your machine that will help in debugging this issue.