So, you put an Eprom in backwards? Chances are this Eprom is damaged and should be replaced - so put the old Eproms back in as you did and order a replacement Eprom - explain about the backwards label, perhaps the vendor will honour their work and send you a free replacement.
As for the game not working now, I would check for bent pins on the Eproms you put back in, this is the most likely cause. Of course you may have installed an original Eprom in backwards too, so check that while you are at it.
John :-#)#
www.flippers.com