Let us first make sure that you do not have a pile up of preview files and conformed video and audio on your computer hard drive.
In the Adobe Folder/Premiere Elements/11.0, by default in Documents(Windows), see what is piled up in the Adobe Premiere Elements Preview Files Folder and the Media Cache Folder. The contents of each can be deleted. The Media Cache at that location will have conformed audio files (cfa and pek), and more conformed autio will be automatically regenerated if and when needed. Deleting the preview files will mean rendering Timeline files again if you need a best possible preview.
Also, go to Edit Menu/Preferences/Media - Media Cache Database - to find a path to the conformed video (.mcdb). Hit the Clean button there to get rid of them. Like the conformed audio, these files will be regenerated when and if needed.
Good idea to optimize your computer. Many including myself included in routine computer maintenance the cclearer for regular and if necessary registry cleaning.
Have you installed any new programs on your computer?
If computer optimization has not impact, let us try flushing the preferences...in Windows 7 or 8 64 bit..
Local Disk C
and in the 11.0 Folder is the Adobe Premiere Elements Prefs file that you delete. If that does not work, delete the whole 11.0 Folder in which it exists.
Remember to be working with Folder Options Show Hidden Files, Folders, and Drives active so that you can see the path described.
How long has the issue existed...just today, yesterday, last week? Depending on the circumstances, you could try a System Restore, but I think that I would prefer what I described above before that.
Please review and then let us know the outcome.
Since you say that this issue is happening with old and new projects, I hesitate to post Adobe information on Damaged projects, but I will post it anyway - for future reference for for now as it turns out.
I would also investigate your video driver, as an obsolete, or bad one, is a major cause of PrE to not launch.
- What is your video card's make and model?
- What is the version and date of the installed video driver?
- When you check on the mfgr's. Web site, is that the very latest version? [Do not trust Windows, or any driver utility to tell you if you have the latest - check for yourself.]
- If not the latest version, download, install, then reboot and test.
Even simple Windows updates can render video drivers obsolete, and PrE must interface with them, more than most programs.