I dealt with this a while back and re-encountered it tonight while getting things in order on a new W2K3 Server.  Blog use #204: record a VS.NET configuration procedure you've used in the past but have since forgotten.

I like to make my c:\documents...\myaccount\my documents\visual studio projects folder a share, as in \\server\vsnet.  Only problem is that VS.NET needs to fully trust it to compile the app and displays the following:

God bless newsgroup contributors everywhere, in this case, John Eikanger of MS VB Support who provided the command line sweetness:

C:\Documents and Settings\me>caspol -m -ag 1.2 -url "file://server/share/*" FullTrust

Worked like a charm.  Full google thread located here.