to get the best quality transfer with any type of tape these are the things to keep in mind.
Fresh tapes... yes you should only use Brand New tapes in any deck or camera... NEVER re-use any tape, this only will dirty the tape heads, rendering your camera or deck useless...
Secondly, if the tape heads are dirty then, get a tape head cleaner "tape" and let it run in the camera for only 3-4 seconds.... if you do this more then 4-5 times you've just lost your tape heads... because the tape head cleaner basicly Scratches "delecately" the tape heads to clean them....
ALSO something to remember, ALWAYS but ALWAYS STICK to ONE TAPE BRAND... if you buy Fuji Mini DV tapes... then ALWAYS buy Fuji Mini DV tapes! The reason why is because, every tape has a different type of silver haliad on the ribbon of the tape. If you take a different brand, or for that matter different quality tape in the same brand, then that is a different Silver Haliad... What happens here is, there's a little bit of the particles from the tape that leaves a residue on the tape head. If you use a different tape afterwards, that silver will collect on to it as well, and there is a good chance of creating a type of Gumming effect..... THUS rendering your tape heads dirty on your deck/camera.
SOOO that was a little tape head/tape info session that will hopefully help your bad transfer problem... if it keeps at it try different softwares, and make sure you have NOTHING but NOTHING else but your Editing program running, or else you can get drop frames if the computer is processing stuff at the same time.