upgrading to autocad lt 2014

I recently installed Autocad lt 2014 on my computer with intel R core TM i5-3450 @ 3.1 with a pny ge force gtx650 w/ 1024 mb gddr5.  When I open one file the move and zoom wheel on the mouse operates smoothly.   When I open the second, third  and so on files they operate in a slow jerky method.   I was told that my system would clearly run LT 2014.   When I tried 2013 lt I didn't have this problem.   Is there something I need to change on my computer.  Thank you/