If I understand you right, your problem is that MED worked fine for you until a certain date, and from then on did not work anymore. If so, then obviously at that date something happened or you did something that damaged your MED or otherwise prevented it from working.
Well, I can't fix whatever it is what you did, unless you send me your PC. But before that, please download again the most recent MED and associated files from here:
http://www.coniserver.net/down/med.zipUnzip this and copy the files in your Gamestudio folder. This at least ensures that your MED is up to date, and the files are not damaged by a virus.
