Welcome to the forum.
As I am not sure what you are working with, or what the Project Preset is, perhaps it's time to post details. This ARTICLE will tell you what would be so very useful.
Ok system...3ghz dual processor...5 gig ram ddr3...2 terabyte hd space spanned over several drives.. OS win xp pro 64 (yes an odd ball one that I regret buying)
I recorded movie with nikon d5100
Project opens as dslr 1920 or something similar
These saved notes are about different models, but reading MAY help
Nikon DSLR stutter http://forums.adobe.com/thread/889477
Just changing the extension from .MOV to .MPG corrected my audio issues!
Wow that was frustrating, but glad it is over and now I will attempt to make things nice!