The Collaborative International Dictionary of English v.0.48:

Untalented \Untalented\
   See talented.

WordNet (r) 3.0 (2006):

untalented
    adj 1: devoid of talent; not gifted [syn: untalented,
           talentless] [ant: gifted, talented]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "untalented":
   amateurish, brainless, foolish, headless, ignorant, incapable,
   incapable of, incompetent, ineffective, inefficient, inept,
   inferior, insensate, irrational, lackbrained, lean-minded,
   lean-witted, mindless, not bright, of little brain, pea-brained,
   pin-brained, reasonless, semiskilled, senseless, slackminded,
   slackwitted, unable, unable to, unaccomplished, unbusinesslike,
   uncoached, unendowed, unfinished, unfit, unfitted, ungifted,
   uninitiated, unintellectual, unintelligent, unpolished, unprepared,
   unprimed, unprofessional, unqualified, unreasoning, unschooled,
   unskilled, untaught, unthinking, untrained, untutored, unwise,
   witless