First of all I would suggest just recording at 1440x900. You're not gaining any extra quality by recording at a higher resolution than what the game renders at, and you're actually hurting encoding performance as well as making your video files larger than they need to be.
Secondly make sure that you don't have clipping enabled in the Movie settings tab and that all the values for Margins are set to 0. When enabled, clipping defines the rectangular region (in absolute pixels) of your screen that is actually captured. Margins does something similar, but it defines the regions at the edges of your screen that are excluded, in units of percentage of total screen width/height.
Facebook
Twitter