the slow motion parts your seeing is it during a complex image i.e. lots of moving small objects like palm tree branches moving or sand particles blowing?
Only it could be that the image requires rendering or your Mac needs more RAM allocated to picture playback or on capture, is it always in the same place? Is it an HDV file 1080i or a 720P as the 720P will also give you this shuttering effect in some cases.
Just curious.
Rgds
gday