When you import source media into a project, all you get in the project are copies of those originals which remain on the hard drive save location. But, the project's copies need to trace back to those originals at the location where they were when first imported into the project.
If you move, delete, or rename files and folders that went into the project after the project is saved closed, you will end up with media offline situation when you go to reopen that project.
Another possibility is that you store you source media on an external hard drive, and the external hard drive has malfunctioned.
Your way to recover from the media project disconnect is to use the "Where is the file ______?" messages to reconnect the project at places where you know the media are. One at a time operation. If you get lucky, several of the reconnects may trigger the rest to reconnect. If external hard drive involved in all this, then repair the external hard drive or store your source media elsewhere for new reconnects.
Please consider, supply more details, and then we can decide what next.
Any questions, please ask.
Thanks ATR. Yes, I do store the video files on an external HD(s) but there is nothing wrong with these drives as I can retrieve any number of other files off of them.....I'll have to fool around with it to see what's going on. So, in light of all this, how should I save my pending projects?
The external hard drive might be OK except that it may be changing drive letter which may not make a difference to some programs, but it does to Premiere Elements. The copies of the originals in the project need to trace back to the originals where they were at import (down to the drive letter).
As a mini test run, create a new project, import your source media, and then open and close the program several times to assure that it opens and closes properly. Keep track of the drive letter of the external hard drive all this time.
As a cross check, put some video at another location (off the external hard drive) and import them into a new project and determine the frequency of Media Offline problems.
In any of this problem, have you lost files from your computer, or has the issue been confined to the Premiere Elements project and its connection to its imported files?
Please consider and supply more details.