My PC doesn't import movies from GH3

If he is doing the same procedure as used on the GH2 it should work except I suspect he have been using 50 / 60 frames per second mode (which the GH2 does not have) and the software he is using does not show this high frame rate. Only a limited amount of software for now will play these files.

I suggest he checks the settings in the record quality section of the menu and selects 24 / 25 or 30 fps, shoots some video and try that in the PC.

Final Cut Pro and I suspect Premier Pro will show 50 / 60 fps but I'm not sure what other software will.