Change the battery on the prism card, then reprogram the game with the latest software version. You have probably just lost the game program code which is stored in flash memory on the prism card. I just dealt with this on my machine because I wanted to play a RFM playfield on my SWE1 and only had the daughter card to swap (so my machine was trying to run RFM roms with SWE1 game code) but a dead battery would probably cause the same thing. The game program is installed on the prism card flash memory and the daughter card only contains basic ROM data for a pre-release version of the game, graphics and part of the sound. The game is designed to continue to run and be playable if it loses the flash code, but it's certainly not enjoyable without the sound. If you turn on your machine and get a pre-release version of software (I was showing version 0.8) with no sound and a checksum failure for ROM 109, then that's probably your problem. You can get more info on the solution at my post on the subject. Good luck.