Bob Brumfield and I spent about 4 hours yesterday fighting, identifying and then documenting a bug in the BizTalk 2004 Schema Compiler.

Here's the gist of the matter:

You have a schema project called Bug.Demo.btproj and the namespace called Bug.Demo. In the project, create a folder called Bug. So the namespace for items in that folder is Bug.Demo.Bug, which should be a legit .NET namespace.

To that folder, add a schema called Foo. Then add another one called Bar. Open Bar in the BTS Schema editor. Add an XSD Import that references Foo.

Compile.

BLAMMO!

Now go read Bob's post for more detail and screenshots.