Jon,
The forums are swirling with desperate people with possible fixes that take a lot of time and might break things further. Microsoft would vastly improve on its public relations image if it only added a few operating system specific trouble shooting steps that the end users could try. First of all there is no distinction made for the different operating systems, vista 32, vista 64, windows 7, window 8. Secondly microsoft has provided no information to allow the more technically conversant people help triage the problem. It would help to know HOW microsoft actually consumes the guide data in WMC. It uses a program that normally outputs an xml file, but WMC does not seem to use it in the same way. The usual xml file is not there. A diagram of how the process is supposed to work, and steps to determine what in the line of steps is broken would be helpful as well. We could then give your team that is fixing the problem more useful data than that allowed in the very confusing and limited "community" input form. I thought that form was broken because it did not offer me any option that seemed to match my problem. The default empty drop down option had NO fields to fill in on the form. It is a very badly designed and confusing mechanism for anyone to have to use for report problems. No wonder some of the comments I have seen say they can't report their issues because the reporting mechanism is broken.