Try to re-register the DLL-file. Open first command prompt from "Start"-button at lower left corner in Windows. Select "Run..." and type cmd and press enter. You should have command prompt open. Now navigate to folder where classlibrary2.dll is OR enter the full path for the classlibrary2.dll. Then re-try C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\regasm /tlb classlibrary2.dll (or <fullpath>\classlibrary2.dll). If any error occurs, you should now be able to see the whole error message.
Before you do that, check which version of .NET you are using (compiling your DLL). I assumed .NET 2.0. If you're using some other version, change "v2.0.50727" accordingly, like "v1.1.4322" for .NET 1.1.