I've been running into an error in Visual Studio .net 2005 when referencing the obelisk web services.
The custom tool 'MSDiscoCodeGenerator' failed while processing the file '...Reference.map'.
There wasn't that much online about it. One of the better posts I found was here:
http://forums.asp.net/t/986668.aspx
But the solutions posted didn't fix my issue. One method that I tried and seemed to work was to create a new project in VS.net and reference the web service there. Then all the files that are created (.disco, .wsdl, reference.map, reference.cs) I copied over into my broken project. Then I went in and edited the namespaces and project names because they didn't line up. Once I did this I was able to get it to compile, and even hitting "Update Web Reference" works well now. I wish I could figure out what was causing this issue, but it seems to happen perpetually only in this one project, so something on the project level must be corrupted. At some point I will likely create a new project and import all my files to it so the project itself gets reconstructed, and hopefully the issues are cleared out at that point.