It's probably because you simple have too many animations installed...the game will stop loading once you hit a particular limit...even with FNIS XXL...I've played a lot with this to find optimal load combinations...If running OSEX as well (which runs outside of Sexlab), you'll find your bandwidth consumed quickly...mods such as OSEX, Devious Devices and especially the Funny Biz packs can stress your machine...it's gonna be trial and error, try disabling the packs you can live without one at a time, rerun FNIS until you get to a point where the game will load...that's your best bet