Freezing when going to idle

When I leave my machine for 10 minutes with the task manager open, I see Microsoft common language drastically increase in memory use to 99% and cause the computer to freeze. Having googled it, ngen.exe in the Microsoft.net framework seems to be the culprit. I have tried using the executequeueditems command to try and clear the backlog, but this also causes a freeze. Any help would be appreciated