I agree with benjiboy. Popping slides is an old problem with slide projecting. Various manufacturers tried to come up with glass-less solutions that allowed more movement of the film inside the frame so the film can expand without bulging/popping. But in my experience only the glass slide frames solve the problem. The Gepe AN glass frames have anti-newton glass (=slightly matted) to avoid anti newton rings and don't seal the film completely from the air which supposedly prevents mold on the film in the long run. The Gepe glass frames are more expensive but in my opinion well worth the money.

Also available here.