I've suggested to the user to convert to a different format but is not a popular option. So am trying to find out whether APE can be setup to preview these files correcctly.
Assuming you have rendered them (hitting Enter key on your keyboard) and you are still having issues you could go to the Adobe Elements 4 folder in your "Program Files" folder and open the "Plug Ins" and "en_US" folders and move the file called ImporterFastMPEG.prm to your desktop. See how they work then... if no better then just replace the file.
Depending on where these MP4s are coming from, you may NEED to convert them.
If they are AVCHD video files, then Premiere Elements can edit them in their native format, if your project is set up properly.
If these are MP4s, on the other hand, from a Flip or other flash-based hi-def format, they are not compatible with the program and will need to be converted to an editable format.
Ok thanks for the info guys
My original recommendation was to convert these but as mentioned wasn't the most popular option.
I've found some other threads on here in regards to a similar problem with Samsung cameras and APE 4. These also mention that the files need to be converted to a friendlier format before importing.