The Collaborative International Dictionary of English v.0.48:

Upsetting \Up*set"ting\, a.
   1. Conceited; assuming; as, an upsetting fellow. [Scot.]
      --Jamieson.
      [1913 Webster]

   2. such as to disturb the self-possession of; unnerving;
      causing mental distress; as, the sight was an upsetting
      experience.
      [PJC]

WordNet (r) 3.0 (2006):

upsetting
    adj 1: causing an emotional disturbance; "his disconcerting
           habit of greeting friends ferociously and strangers
           charmingly"- Herb Caen; "an upsetting experience" [syn:
           disconcerting, upsetting]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "upsetting":
   agitating, annoying, baffling, bewildering, bothering, bothersome,
   breathtaking, chafing, charged, cliff-hanging, confounding,
   confusing, discomposing, disconcerting, dismaying, disquieting,
   distracting, distressful, distressing, disturbing, electric,
   embarrassing, enigmatic, exciting, exhilarating, fretting,
   galvanic, harassing, heady, heart-expanding, heart-stirring,
   heart-swelling, heart-thrilling, impressive, inflammatory,
   intoxicating, intricate, jarring, jolting, maddening, mind-blowing,
   moving, mysterious, mystifying, overcoming, overmastering,
   overpowering, overwhelming, perplexing, perturbing, piquant,
   plaguing, problematic, provocative, provoking, puzzling, ravishing,
   soul-stirring, spirit-stirring, stimulating, stimulative, stirring,
   striking, suspenseful, suspensive, tantalizing, telling, thrilling,
   thrilly, tormenting, troublesome, troubling, unsettling, worrisome,
   worrying