OK, this is weird because I can't reproduce it myself. However judging from the error message I think I know what it is. I've done what I hope fixes it and built new editor EXEs:
Drop the new .exe in to your install folder and run it - does it fix the problem? I need to check with you guys first since I can't seem to reproduce the issue, but since it sounds quite serious if the fix works I can have a new release out in a few hours.