I don't know when started, but a few days ago my Premiere Pro and After Effects don't recognise MPEG2 files.
When I try to open a Premiere Pro with a MPEG2 file in it: "This project contained a sequence that could not be opened. No sequence preview preset file or codec be associated with this sequence types"
Just to verify that the files are not corrupt...
Report back with the codec details of your file, use the programs below... a screen
shot works well to SHOW people what you are doing
For PC http://mediainfo.sourceforge.net/en or http://www.headbands.com/gspot/
For Mac http://mediainspector.massanti.com/
Also... does your PPro show the option to de-activate? (having the de-activate option available means your version has not "lost" activation)