The Collaborative International Dictionary of English v.0.48:

Demented \De*ment"ed\, a. [From Dement.]
   Insane; mad; of unsound mind. -- De*ment"ed*ness, n.
   [1913 Webster]

Jargon File (4.4.4, 14 Aug 2003):

demented
 adj.

   Yet another term of disgust used to describe a malfunctioning
program.
   The connotation in this case is that the program works as designed,
   but the design is bad. Said, for example, of a program that generates
   large numbers of meaningless error messages, implying that it is on
   the brink of imminent collapse. Compare wonky, brain-damaged,
   bozotic.


Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "demented":
   abnormal, bereft of reason, brainsick, crackbrained, cracked,
   crazed, crazy, daft, delirious, deluded, deprived of reason,
   deranged, disoriented, distraught, flighty, frenzied, hallucinated,
   hysterical, insane, irrational, loco, lunatic, mad, maddened,
   maniac, manic, mazed, mental, mentally deficient, meshuggah,
   moon-struck, non compos, non compos mentis, not all there,
   not right, odd, of unsound mind, off, psycho, queer, reasonless,
   senseless, sick, stark-mad, stark-staring mad, strange, tetched,
   touched, unbalanced, unhinged, unsane, unsettled, unsound,
   wandering, witless