If you are having problems with a Genesis patch it is most likely a ROM format problem. Most patches require your ROM to be in BIN format(and not SMD). A utility named SMD.COM(which is mysteriously not on our site at this time.) can convert it for you. This is a DOS utility, so in the command prompt type: "SMD.COM /CB ROM.SMD" or whatever your ROM is named. Don't actually type "ROM.SMD" unless it's actually NAMED that. The "/CB" switch will make a copy of your ROM called, in this instance, ROM.BIN. Try and patch that ROM instead.

Still having problems? A lot of Genesis games will lock up if their checksum's been altered. Gens and Kega Lazarus both have an "Auto Fix Checksum" option, which will fix the problem.