Where are the source videos for your projects? Were they moved?
Thanks for your response. Video footage was taken with a Sony Handycam GDR HW66. Downloaded as a MTS file (as least that is what it describes the file type as in properties) and dropped into Elements. Hasn't moved from there. Pretty much the same as I have done with videos prior to this issue and the same as I have done for the Test video subsequently - all of which had no problems.
I'll try again..... Where are the .mts files?
Video files are never "in" Premier Elements. They are in a file folder somewhere like C:\myfiles\videosclips. When you make a video you "Add Media" to the "Project Assets". That process only registers where they are. The "Add Media" dialog has a lot of options and may actually copy files from your camera to your computer. Or you may use other systems like Windows Explorer, Lightroom or Organizer to do it. One way or the other, the video clip (.mts) files are put somewhere.
If that "somewhere" changes or goes away, Premier Elements tells you "Media Offline". Is it on the camera that is now unplugged? Is it on a external HDD that is now unplugged? Sometimes people mistakenly "clean up" their computers by removing what they think are unnecessary files because the files are "in" Premier Elements.
Can you verify that the source files are where they were when you started the project?
Thanks again for taking the time to provide me some feedback. I was going to say that nothing has changed but on thinking about it I I possibly know what has happened. In answer to your question I download the MTS file onto my C drive. What I did this time however is I put some of those MTS files into a temp file so I could more easily chronologically order the video. Once I had put those files into Elements I deleted that folder. Those particular MTS files were still elsewhere in C Drive but I suspect given what you are saying that may have been enough to upset the apple cart. This really only related to the one video project I was working on but all six (or so) appear to have been affected. As mentioned a later test video has worked fine. Does this sound like it could be the cause of my issues?
Yes, that is exactly what happens when the video files move or get deleted.
Close the project and reopen it. There is a dialog box that shows up asking where the file is. Locate the folder and all will be well again.