mobile cpus especially those weak ones tend to have problems with 720p30
then again no idea for what reason changed your scene buffering time (latest default would be 700)
also make sure to either disable aero and use monitor capture and NO window capture
or leave aero enabled and use no monitor capture (except if you are on windows 8 then it doesnt matter since aero actually works good)
if this fixes it already then you are fine if not try the superfast preset if this doesnt work either then go back to veryfast preset and downscale to 540p