failed to start

I'm trying to install the lastest Itunes update, but it won't finish. I get theis message: Service "Apple Mobile Device" (Apple Mobile Device) failed to start. Verify that you have sufficient privileges to start system services.

I've never had a problem before, and I was listening to Itunes just before it asked me to update. Any idea what the message means, or how to "verify that (I) have sufficient privileges"?