exactly - a normal frame rate is 30fps (actually it's 24, but 30 is also expectable), so your computer is try to play all 60 frames in the same amount of time as it would try and play 30 frames - so it looses some of them, which is the skipping. So what you need to do is convert the file to half speed (so now it's playing in a 30 fps mode) and then when you save the file you need to make sure the frame rate is 30fps (all programs kinda do this differently, but usually it's under some sort of advanced settings). Then when you play it, the computer will realize it's a 30fps file and wont skip.