Works on Dev, not on Server!!

I'm having a strange error lately. A function that was working fine on my web app is now crashing for no apparent reason. It works fine on my local machine, but on my server I am getting this message:

"Object reference not set to an instance of an object"

followed by:

Project.Module.Function(Int32 Variable) in C:\Documents and Settings\user\VSWebCache\PC234\Project\Module

This seems very bizarre to me. What is this "VSWebCache" and how does the server know about my local PC? Why is it trying to look there to find the function??? I have uploaded the binaries to the server; everything has been working fine until recently. Does anyone have any ideas?

P.S. I am using ASP 1.1 and VB.NET/VS 2003