Newbie question: "VSHost is not responding" error

This is my first Windows Client - WCF program. I'm generally following the pattern shown in Beth Massi videos and developing with VS2008 and SQL Server 2008. I have completed a simple application on my desktop (Vista Ultimate). When I run it in debug mode it runs for a while and then I get "VSHost.exe is not responding" and the application freezes up. I run "clean" and update the references and it starts running for a while and then the error pops up again. I'm used to client server development and never run into anything like this. What's happening and how can I fix it?

Thanks