Compatibility????

Question

Afternoon, I have been working with an application SDK for a while now and recently upgraded to .NET 2003. In doing so, the original sample application within the SDK still works, but as soon as you load the original source from he SDK and build the solution, the application no longer functions. Is there something I need to do, or direction I should be looking, or is it probably just an issue with the project now being converted to the .NET 2003 format? This is a .NET remoting application which comunicates with an existing application running on a server. The app on the server has not been modified at all, just the client. Also, can anyone give me some pointers on the debugger. I am looking for any information that can give some of the basics and how to's for debugging applications. Thank you..