For some time I was getting problems with recording TV on VMC and I have now found a solution which I thought I would share.
The problem showed itself in a number of ways and got worse over time. Soon after starting VMC a message would popup saying a critical failure had occured in Media Center but it continued working OK. Sometimes recordings were split into several small chunks and would sometimes fail before the end. Sometimes a scheduled recording would not take place, although it would show as recording at the time (the red dot). When I tried deleting scheduled series from the list they would not delete. I even had a programme showing as recording even though it had finished recording the previous day and it still showed as recording after re-booting. Generally it seemed that the scheduled recording data was corrupted.
This can be fixed by closing VMC and renaming the file c:\ProgramData\Microsoft\eHome\Recordings\Recordings.xml (and also the Recordings.xml.bak). Alternatively, just delete the files. On restarting VMC, it will recreate these files but will obviously remove all scheduled recordings. The recordings will need to be manually added back into the schedule.