My first camera which had this problem was my N90S and I got it usable by simply removing the goo down to the plastic back with alcohol. I didn't worry at that time since this is a widely known problem with that particular model. However, when it started to occur about 3 years later in the Maxxum 7 and N80 I got worried. I would hate to have this happen to my Maxxum 9 for instance! I followed Mark's link on Renaissance Wax, but it contains petroleum components which are generally destructive of rubber. Any other ideas?