Windows 7: Gaps in wtv recordings

Most of my recent wtv recordings seem to have "gaps" in them. On playback, they will play fine for a while but then I'll get the "Video Error, files needed to display video are missing..." error message and playback will stop. If I am fast enough I can skip over these "gaps" and continue watching the programme.

No errors are logged, either in the recording history within Media Center, or in the event log.

I have tried converting the wtv files to dvrms but the resulting dvrms file stops at the first gap.

I believe this is happening on mulitple channels.

The gaps generally occur just before a commercial break, however this is not always the case.

In a longer recordings the gaps become more frequent towards the end of the file.
My question is in two parts:



1. how do I prevent this happening on future recordings?
2. is it possible to repair existing recordings?

Windows 7 32 ultimate.