I don't know if I might be wrong about this - but didn't have the FBANext releases (Xbox360) prior to 0.2.97.27 the ability to create a CLRMame DAT-file from the menu?
I've rebuilt my sets from the 0.2.97.27 (Windows) Release and FBANext (Xbox360) tells me that some roms aren't right when I try to start a game (I think it was Mario Bros in particular)
Thanks!