Grrrr ... I was afraid of this. Had the same problem with PE, market worked for most but a few had it FC. Thought maybe it was a ROM thing, but it appears to be a GB thing. I have this very same market apk in two froyo ROMs without any problems ... looks like GB don't like its market messed with.
Will probably need to restore a backup with a working market before trying the theme again. I will do what I did with PE GB, make a marketless version of the theme and offer the market as an "add at your own risk" extra.
Sorry for your troubles!!!
Sent from my Incinerated DROID