I have Windows 7, and using WMC and Movie Maker 2011.  I had no problem loading HD .wtv files into MM until recently.  I think the last automatic update did something to stop it working.  What happens is that less than 5 min into "preprocessing" the HD file in wtv format, it crashes with yellow bang.  Claims the file is corrupted.  But the last 4 wtv files I recorded from HD TV all does this.  I also moved one of the files to a laptop I have MM 2011 with no update, and it does the same thing.  Seems like there was some update to WMC wtv file format, maybe a codec, that MM doesn't understand, and there was not a corresponding MM 2011 update.  These HD files are usually over 10GB.  LD files are < 5GB and don't require preprocessing, and they work fine.

Don't say "just update to MM2012" because it doesn't work on my system, apparently the HW is too old and 2012 doesn't support it, I had all kinds of issues with 2012, and went back to 2011 upon advice of an expert, which solved all the major issues, except now I have this one.

I could revert to older WMC (before update) if only I could find out how, and then turn off autoupdates.  Actually I do have autoupdate turned off, so I don't know how it's updating.  I just know it does, because about every month I come in first thing and the system has rebooted, and a popup tells me that Windows has been updated.

I just wish I could fix this problem.

Tdidymas