I recently acquired a Mac Plus that I have restored to working condition (repaired broken solder joints on the analog board). Today I upgraded the memory to 4MB and had trouble getting the back of the case to go back on. Something seems to be catching on the right top corner (above the battery). I finally got it on once by bumping it just right, but then I took it off again to clean the floppy drive (which won't eject), and now I cannot get it back on no matter what I do. I have inspected the case thoroughly and I can't tell what it might be catching on. The first few times I took the case off I didn't have any trouble but this time it just refuses. Any ideas?