I installed the VPN client 5.0.00.0340 on my laptop. I also run iTunes and listen to music (this is how I detected the problem).
After installing the client I noticed that iTunes would cut out at about 10 to 30 second intervals. I removed the VPN client and iTunes was smooth again.
I look at Task Manager and the only process that comes close to coenciding with the iTunes drop out is called System with a description of NT Kernel & System. This is a pretty basic process that is running, so I am stumped.
When it happens this task taks 100% processor for a few seconds.