Would OIS cause footage to "skip" in 720/60p hand-held? I thought it is an export issue, but when I looked through the original footage it does it while showing runners in motion. I was filming hand-held, no tripod used.

Here is the link to the video on youtube ( I am out limit for vimeo for the week). The file was unedited. What is causing the change in the speed of recording?

Here is a link to the vimeo, where you can download the original file. If anyone could tell me what happened, so I could avoid such situation in the future.
JVC GY-HM100 recording issue on Vimeo

Are you talking about the motion of the runners.
I donwnloaded the clip from vimeo, and it did not play very smoothly. Have you burned a Blu-Ray and watched it on a TV?

I shoot 60p also, and I have noticed it does not look as "smooth" as 60i at times.

At second 4 and then 6 you can see runners change the pace- looks like they stop for one frame- all of them, not just one.

Verify the SDHC brand - looks like camcoder was not able to record at full speed and skipped frames.