Error: Unable to get project file from the Web server?

[Andrew]

Hello,

I installed MS WSE 2.0 SP2 Hands on Lab 34 - Security. However, I could open
all solutions using VS.net, except the
CS\Exercises\A\before\SecureInvoiceA.sln. For this solution, I could not load
its SecureInvoiceServiceA.csproj and I got an error: Unable to get project
file from the Web server.

I could not figure out what's wrong with this solution since I was able to
load other solutions of the lab.

Any ideas or suggestions? Thanks a lot for your help, this drove me nuts.