What computer operating system is your Premiere Elements 8 running on?
Are you working from the 8.0.1 Update of the program?
Do you have the automatic Background Rendering and AutoAnalyzer features disabled?
When did you use the program last for a successful video import, edit, and export?
For starters delete the Adobe Premiere Elements Prefs file and, if necessary, the whole 8.0 Folder that the Adobe Premiere Elements Prefs file exists.
Assuming Windows 7, 8, or 8.1 64 bit....
Local Disk C
and in the 8.0 Folder is the Adobe Premiere Elements Prefs file that you delete. If that does not work, then you delete the whole 8.0 Folder in which the Adobe Premiere Elements Prefs file exists. Be sure to be working with Folder Option Show Hidden Files, Folders, and Drives active so that you can see the complete path cited.
Please review and then let us know the results.