It is widely known that the black outer rubber band on the eTrex models is not fixed very well. The adhesive tends to loosen with time.

I solved this problem this way: First I took off the rubber completely. Then I could wipe the old glue off using a piece of cloth and some petroleum ether. I left the transparent film in place. After that I glued the black rubber back on with a thin layer of normal sanitary silicone. Works like a charm!