I was changing my 47s Quark from an AA to a CR123 body and tried turning it on. Nothing. I opened it up and realized I put the RCR123 in it the wrong way around. I turned the battery around and tried again. Nothing. DID I JUST FRY MY LIGHT?!? Can't be. The Quarks have reverse polarity protection, right? Why it it not working then? I think I might have smelt something burnt but it may have been my mind playing tricks on me. I had to go out and couldn't play with it more at that point. But I was worried and was looking on my phone for how much a spare tactical head went for theses days. ($39 ) When I got back home I tried it again, nothing. I tried it with the AA body and WE HAVE LIGHT. AAx2 body also working. But when I tried it with the CR123 body again nothing. I tried changing batteries. Then back to AA. After another few assemble/disassemble attempts it started working on an CR123 body. But I still don't understand what happened. Why was it dead on a CR123? Did anyone have this happen to him/her?