Probably indeed a problem with the hack.
So it looks the camera was perhaps put off after a longer clip at a high data rate, and the index was not finished.
After a long recording, make a very short recording (just 1 or 2 seconds).
Probably QT will not open the file. I once had such a clip (with FCP 7 then). Premiere also didn't recognize the clip. But Toast did. Open Toast in the media conversion window (or so, I have a german version). Drag & drop your clip into it, export as QT, ProRes (gear icon lets you set export codecs). My problem was, I could only export the audio as an extra clip (make it Aiff) and had to synchronize both in the NLE.
If this doesn't work, either upgrade to 10.8 (AVCHD is played back by QT without conversion, the upgrade is safe) - but I bet it won't work either, because still OSX doesn't like .mts without or with wrong metadata.
Or take your card to a windows computer, where you export both clips with highest quality settings of H.264.