My boss has been having this annoying problem for a while now. She will be typing in an Outlook email and the system will hang for a while and then process what she typed.
Seems to be related to the Telephony service starting and stopping on a regular basis. I set the service to start Automatically, which you would intuitively think makes the service start at system startup and stay up until the system is shut down, but no. It starts and stops as Windows thinks it should.
Based on her use of Outlook and how the hangs happen (she typically goes into Contacts to look up a phone number then a few minutes later goes to write an email and the system hangs) as well as on the event log (the Telephony service keeps starting and shutting down), the Telephony service is the only thing that I can put my finger on as contributing to the problem.
As someone who's been doing Desktop Support for a while now, the old "my PC is running slow" complaint is one of the more dreaded things that a user can say since a lot of things can cause this and it may just be unreasonableness on the part of the user (some things take a long time to do even on a fast PC), so troubleshooting that sort of issue can be a real pain.
I just hope that I find a fix for my boss's issue soon.