Looking at the event viewer, I saw a few messages about

http://alan.lamielle.net/2009/09/03/windows-7-nonpaged-pool-srv-error-2017

I googled and found this:

http://social.technet.microsoft.com/Forums/windows/en-US/30919e4f-6810-48d6-8769-2cff61f07544/event-id-2017-the-server-was-unable-to-allocate-from-the-system-nonpaged-pool-because-the-server?forum=w7itpronetworking

I am trying the settings it suggests and rebooting.