Steve,
First, we need to know more about what you are doing, how your are importing, and do you have Adobe Creative Suite 5.5 Production Premium for Windows or Premiere Pro CS5.5 or what.

There are several ways to import, but I am not sure this is your problem and if it is I will help you there.  First, if you have the Suite, you can import and do much of your editing in After Effects.  When importing in After Effects you want to go to:
After Effects > Composition > Composition Settings > and use the preset HDTV 1080 29.97.  Make sure to check the box for Lock Aspect Ration to 16:9.

If you are importing into Premiere Pro CS5.5, I use the Sequence Settings for AVCHD 1080i square pixels 29.97.

Now here is the important thing, in editing mode, the picture quality is not greatest but when you send it to Encore to burn to a disc, you will find a much better quality picture.

So I need much more info from what and how you are doing things.  Maybe even step by step so I can see where the problem is.

Photo_85

When you copy the files from your internal memory to the SD card, the files are MTS files and when transferred to your computer it should remain the same.  Windows Media Player will play should play the MTS file.

Is your software copies or Genuine Adobe Software?  Yes, it makes a difference.