Proper way to import footage
AVCHD footage comes in a complex file structure that contains much more information than is typically found in video clips.
You can work on footage while it's on the storage card. But if there is any difficulty, the first thing to do is to copy the footage onto a hard disk. Be sure to copy the entire file structure of the card instead of just the clips.
Always use the Media Browser in Adobe Premiere Pro, or use Prelude, to import the footage.
http://helpx.adobe.com/premiere-pro/kb/audio-video-glitches-avchd.html