if you have shot in full HD why import it into a 720p Seq, import into a full HD Seq, and later export to the required frame size.
Please NOTE that the PPro CS6 screen may look a bit different (I use CS5)
For CS5 and later, the easy way to insure that your video and your project match
See 2nd post for picture of NEW ITEM process http://forums.adobe.com/thread/872666
-and a FAQ on sequence setting http://forums.adobe.com/message/3804341
Chances are the grain is actually there in the footage, but WMP hides it.
Neither WMP nor PP's own built-in Monitors are designed for accurate display of video, however. You really should be watching on a properly calibrated external TV.
Thanks everyone. I've since noticed Windows Media Player AUTO enhances the video when playing back and therefore not giving an accurate representation of the footage! I've watched the same footage back on QuickTime and the grain is there in the default footage. This confirms there is nothing wrong with PPro, instead stupid WMP doing it's own stuff!!! I've looked around WMP to see if I can turn off any of these auto enhancements but can't find anything, anyone else experiencing the same?
This is not uncommon. It's why you can't trust software players on a computer monitor to judge quality. You really need that external, calibrated TV.