When you start a recording of a currently running program MP will takes up to a minute sometimes to start the actual recording. Sometimes it even never starts the actual reording.
Start TV
Open TV guide
Select a program running currently on a different channel.
record it

MP will now say it is recording it (red dot in the tv guide) but the actual recording is not happening.
Due to these 2 things being out of sync MP can do weird things like unable to stop the recording as it isn't reallyy running etc.
When you restart MP it will start recording imediately.

h4. Additional Information
I found out some extra info connecting this problem more to my system.
When I use my internal drive to record to all works.
When I use my FireWire drive I get this problem.

So, to sum up.
I can record a future program
I can record and timeshift at the same time
I can ff and rewind, all goes fine
This all indicates that the speed of the drive is ok.
It fails when recording a current running show. This makes me think that the problem lies in the part that copies the part of the program allready in the buffer to it's final destination when stopping the recording. This somehow takes too much time or gives some other error (nothing in the log) and this results in only a database entry and no real videodata as the copy of that failed.