My usual disclaimer...I am strictly an Elements Windows user...and I believe you are working on Premiere Elements 11 Mac
Based on your question being a "it worked before but not now" type, I suspect that your issue does not go to use of a tryout version and probably not codec matter. Focus "suspect".
With the assurance that you have the latest version of QuickTime installed on your computer with Premiere Elements 11 Mac, you might consider ruling in or out a corrupted Elements Organizer preference file, the psa.prf. I have no idea where it would be in Mac, but for Windows 7 or 8 64 bit, it is found in the path:
Local Disk C
and in that Organizer folder is the psa.prf file that I delete (some just disable it by renaming the file to something like psa.prfOLD)
And, as usual, to see the path, I need to be working with Folder Options Show Hidden Files, Folders, and Drives On.
Have you tried to delete one of these problem videos from the Organizer (not the hard drive) and then bringing it back into the Organizer from its hard drive save location?
Another maneuver might be to delete the problem video from the Organizer. Open a Premiere Elements project, import the problem video from its hard drive save location via Add Media/Project Assets. Then click on the Organizer Tab at the bottom of the Premiere Elements 11 workspace to open the Elements Organizer. A copy of the import should have been placed there automatically. Is it there? And, how does it play back now?
Just a few thoughts for now.
Thanks...sorted by renaming the preferences file as suggested (I tried removing from catalogue and readding but that didn't work.) For the record, on a MAC, this is located at:
//Users/[User Name]/Library/Application Support/Adobe/Elements Organizer/[Version]/Organizer/psa.prf
The file is re-created on exit from Organiser.
I suppose an obvious question is, why would it do that and how frequently? Given the initial problems I've had getting it going, perhaps it's just one of those things. I'll use the app for a few days and see how it goes. Having restarted
On the positive side, I've now created a working video with titles and transitions etc so things are looking rosy.
Thanks for your help over the last few days ATR, I really appreciate it. You've got me off the ground and running and I was ready to give up if you hadn't given me the useful pointers.