Microsoft's compatibility goal for .NET Framework 1.1 applications is that they should work smoothly on the .NET Framework 2.0 except for a set of documented changes...
Of course, we know that not everything they say happens to be true, but it is normal for me to expect my 1.1 compiled dll to run under 2.0. Actually, it works locally on my machine when I change IIS to framework 2.0, so maybe there is something else we are missing.