Can you please furnish us with the complete specs. of your computer, plus the Project Preset that you chose at New Project. See this article for more details: http://forums.adobe.com/thread/459220?tstart=0
AVCHD (and all H.264 material) is highly CPU intensive, and requires a lot of horsepower to edit.
Premiere 6 is 10 year old software. HDV and AVCHD didn't even exist in 2002.
But if you're talking about Premiere Elements 6 -- there WAS Premiere Elements 6. In order to catch up with Photoshop Elements, the program jumped from version 4 to version 7.
So I'm not sure what to tell you.
Steve brings up an important point. I had just assumed that you meant Premiere Elements 7.0 (as he says, Adobe skipped PrE 5 & 6).
Exactly which version of Adobe Premiere do you have?
If it is NOT Premiere Elements, then I will move your post to the appropriate forum.
1st, you MIGHT be able to edit by using Cineform Neo Scene http://www.cineform.com/neoscene/
2nd, if you really mean Premiere 6, Hunt will move your message to the correct forum