Still no joy. I've checked that the frameworks are installed. I have 1.0.375, 1.1.4322, 2.0.50727, 3.0, 3.5, 4.0.30319.

I've taken out all of my original code and tried to compile it but I still get the same error.

Am I looking at the wrong approach for this?

The reason I'm writing a custom assembly is so that I can create function that I can use across a number of different reports. It seems to be a spectacularly complicated way of creating a library of functions for RS. Have I got the wrong end of the stick? Is there a simpler method of sharing functions?