It sounds like one of the services is getting hung when you try to close it down, and the second time it gets around it.

Gonna be hard to pin down without the "Windows is trying to close such and such a service messages", but you can try to go into the task manager, sort by CPU usage, and see if anything is clogging it down, stop that service and see if that works. That will tell you the service you mave an issue with if it's a service hanging it.