The first thing noticed is that MC5 is a new beast.
Here are some AVCHD files to try.
The first 3 files are mts.
Because MC5 is capable of importing AVCHD files.
Update:
1) The import is slow but the files are coming fine into MC.
2) NTSC clips can't be imported into a PAL project as MC detects the framerate and stops you.
3) Once come into MC they play fantastic.