Astronaut forgot to record "The Sopranos" episode. Ground control sends 8-man team home to make necessary repairs. Mission unaffected.
Astronaut mentions he needs to TiVo "The O.C" episode, flight status is rescinded for bad taste. Mission scrubbed.
Astronaut discovered alien/hentai pornography left behind by previous inhabitants, crew too emotionally disturbed to initiate ascend procedures. Crew stranded on lunar surface.
Astronauts get into fistfight in LM, LM is irreversibly damaged to crashes/cannot ascend.
(yes, I know TiVo or "The O.C." wasn't around then)