dresali: well, it wouldn't allow you to make that first capture either: remember: you can't jump a piece twice, meaning that when you jump to g9, you can't backtrack and jump d6 as well.
So the possibilities are:
27. b10xe7xg9 or 27. b10xe7xb4 or 27. b10xe7xc5

If either one of the above doesn't work, then do send a bug report to Fencer, but I think his implementation is probably sound as it is...;)

vic:
I guess i shouldnt try to read game rules in the middle of the night ;)

Thanks for your help, vic :)