Shutting off the HTPC while a program is recording in TS format probably does break the TS file. I don't use TS, but my understanding is that it records in one large file, so basically you have killed MC while it is writing to the TS file, which will corrupt the file. How much of that file should be viewable I'll leave for someone else, but maybe 25 minutes is the usual time for the TS format? I would expect it to be random actually, or almost all the file, but I don't know.
Anyway, when you have a runaway recording next time, try this to see if it helps.
1. Change to the channel that is still being recorded.
2. Hit the Stop button on your remote.
3. Change to another TV channel (via the Guide or with channel up/down) and view it for a moment.
4. Hit the Record button on the channel playing.
5. Hit the stop button with one minute of starting the new recording.
This should stop the runaway recording, but leave the TS file intact. The short recording you started and stopped should be discarded by MC as it was too short. I think there is a minimum recording time for a recording to be kept, and I think it is two minutes. But I could be thinking of my previous PVR or something regarding that. Whatever, if you get a very short recording, just delete it.
I still have no idea why you get MC hangs. I don't, ever, unless I am doing something really strange on the HTPC, and even then it usually comes back if I wait. Sometimes I need to stop playing everything for it to recover though, and if I have a problem a usually reboot the HTPC to clear out any problems.
I don't know why you get runaway recordings either. I have had a few, and there hasn't been any reason I could identify. They have usually happened when I was doing long recordings though, like for sports events that last for a few hours, plus I have added Padding to the recording of an hour or so.
Keep trying to identify the causes though. It will be something specific, and possibly not caused by MC, but by some hardware, or other software, or the load on the CPU or network or something like that.