What computer operating is involved?
Please give more details....
a. Are these projects opening to the Expert or Quick workspace? Are you saying that, when you hit the play button of the Edit area monitor, the Timeline Indicator does not move from left to right to give you playback of the video and audio in the project's Timeline?
b. Is your video card/graphics card driver version up to date according to the web site of the manufacturer of the card?
c. Does the problem exist with and without the antivirus and firewalls disabled?
d. Can you see any obvious changes in your system before and after the problem set in?
Please give more details. Depending on the details in your reply, we may consider
a. deletion of the Adobe Premiere Elements Prefs file
b. uninstall, free ccleaner run through, reinstall with antivirus and firewalls disabled
Any questions or need clarification, please do not hesitate to ask.