There is a bug with YouTube being widely reported in the YouTube Help Forums where when you upload your video, when it is done, the preview thumbnails displayed are coming from another random video.
The video itself is correct, but the preview thumbnails came from a random third-party video on YouTube.
Here is a screen shot showing during the upload process and when the upload is complete, it switches the thumbnail images to a random set.
David from the YouTube team said, "Yes, this is a glitch in previews only. We are rolling out a fix this evening to address this problem."
So they are working on the fix.
Update: David from YouTube said it is now fixed.
Forum discussion at YouTube Help Forums.