I’ve been using EAGLE 5.11 for a couple years with no problems. I recently up-graded to 6.4 and because it frequently crashed I went back to 5.11. Unfortunately while trying to use 6.4 I made a number of custom parts and several PCBs which will not open in 5.11; I get the message INVALID DATA.
Is there anything I can do to recover these files so they will open in 5.11?