We will need more information to look for the cause of the issue that you are describing.
1. On what computer operating system is your Premiere Elements 10 running? And, what is the video card that the computer uses?
2. What are the properties of the video that you are using when this issue occurs? I am looking for video and audio compression, frame size, frame rate, interlaced or progressive, file extension, pixel aspect ratio.
3. What are you setting as the project preset for this project? The project preset should match the properties of your source video.
4. How are you uploading your Timeline content to YouTube....
a. Are you exporting your Timeline content to a file saved to the computer hard drive and then uploading that file to YouTube at the YouTube web site? If so, please give all the export settings including any customization of the export settings under the Advanced Button of the preset selected.
b. Are you using the program feature Share/Computer/Online/YouTube? If so, what preset are you selecting for this upload?
Please review, supply the requested information, and then we will move forward from there.
Give a link to YT.