I've made an animation in After Effects (no video; all animation) in a comp that's 29.97fps. Even if I force the frame rate to 29.97 in the render queue, the final animation opens as 30fps in Quicktime.
And to confound me even further, if I export an Animation codec of the same video from Quicktime (again, forcing 29.97), it exports a QT with a frame rate of 26.60! Any idea what's going on?
Sometimes After Effects can be a little funny with quicktime. I would suggest updating quicktime player if you haven't, and if the problem persists try downgrading. Find an older version below are two links. If the problem is still there then try reinstalling after effects and if nothing works just export to a different format. An mp4 is more universal than an mov and it also works with quicktime.