Unthinkingbit where did all those changes of your in your last post go?  I looked in your https://github.com/Unthinkingbit/groupcoin for a commit for the last changes but I see nothing changed.  Don't make people repeat work you have already done or prevent them from seeing what you might have done wrong.  push the changes you made to another branch so we can start seeing and using them.  I agree with part of what mark says, stick with the -testnet function first as main has other complexities including check points that are not worth dealing with at this time.  I disagree with mark on the side to keep the same 8 bit header version code on the address.  It is true it will work without change but it adds the posibility that people will try to send BTC or testnet on your version client or other client and wonder why nothing comes out.  I know these specs are working as I'm already minning with these specs now in MultiCoin.   Also why aren't we seeing you Unthinkingbit in the freenode IRC #groupcoin?  head to head chat sometimes makes things move quicker.   Ok I was a bit busy with work on escrow features and had assumed mark could get you going from here.  Oh and I see you seem to want two block chains as I maybe didn't make clear main and testnet are completely different chains,  I did create a secound chain that I published for your -testnet at http://exchange.surething.biz/docs/multicoin/bitcoin.conf.groupcointest  but I thought you didn't want it so if now you changed your mind here it is.  I haven't mined any of them yet and didn't plan to.  I created a branch of your groupcoin at https://github.com/sacarlson/groupcoin with some of the changes that would be needed to run the groupcoin  spec in -testnet mode.  you can force it to be testnet all the time or reverse it to make testnet to be main and later make a testnet that works.  I have now compiled it and tested it to some degree and it seem to be working with your new spec in your code.