Large video files hanging up Windows Explorer

Hello,


I was working with pinnacle studio 14 and all was well and then I went to move some large video files, over 3gb, and then windows explorer starting hanging up in to this, just kept saying calculating. Windows media player will no longer play these large files and now pinnacle cant load them. I have nortons virus and vista 32 sp2. It all worked flawless before now and then brick wall. I have run hardware checkers and scanned with nortorns..nothing amis...Am I looking at some kind of buffer problem and any ideas how to fix it?