This is an ASP.Net error I got while converting a .Net Remoting app from 1.1 to 2.0, and it puzzled me for a while. The conversion had gone fine and everything built and deployed without a problem, but the unit tests I'd written were failing to find the remote service. IIS was being used as the host for a handful of wellknown objects, so I tried browsing to the WSDL and this was the error.
Check on Google and you'll see there aren't any relevant hits, so obviously something strange in the setup of this app. The stack trace (HttpRemotingHandlerFactory - WebServiceParser) suggested ASP.Net was trying to compile the .rem files. I set up a simple Remoting app hosted in IIS which worked in the same environment, and checked to see what was different.
The problem was that the 1.1 app had .rem files saved in the virtual directory of the Remoting service, so the request was finding the physical file and trying to build something from its contents. In 2.0 the .rem files are created on the fly when they're requested, so they get routed to the correct handler. After deleting the .rem files, everything was fine.
Surprising that this hasn't been seen anywhere else, but it's documented now.