Exactly what is INSIDE the video you are editing?
Report back with the codec details of your file, use the programs below... A screen shot works well to SHOW people what you are doing https://forums.adobe.com/thread/1070933 for screen shot instructions
Free programs to get file information for PC/Mac http://mediaarea.net/en/MediaInfo/Download
Does your video use a VARIABLE Frame Rate or a Constant Frame Rate?
Premiere Elements 10 on Windows 8 64 bit...
Several angles on the issue that you present...
What is the video card/graphics card that your computer uses? If NVIDIA GeForce, please stop and let us know.
There is a known issue with Premiere Elements 10 on a computer that uses a NVIDIA GeForce card. In these instances, the answer is not to
update the card's driver version to the latest version, but rather to roll back the driver version to May 2013. Often the old NVIDIA GeForce driver versions do not go back far enough to resolve the problem. See
If your computer does not use a NVIDIA GeForce, that major issue can be excluded from the troubleshooting.
Then we need to know the properties of the source files that you are importing into the project. You can use video audio properties readout programs to obtain that information, but a quick and effective way would be to give the brand/model/settings of the camera that recorded the video. We can get the important information that we need from that type of information.
Is this a "it worked before but not now" issue or a "it never worked before" issue?
Please review, consider, and give more details.