Newer updates to Mac OS X Leopard seem to have an interesting problem with their spelling databases: they include words that are most certainly wrong. The problem first appeared in 10.5.2 (U.S. English), and has not yet been corrected.
Canspice.org points to an Ars Technica discussion from March highlighting the misspelling knswledgable. If you open TextEdit, for example, and intentionally misspell the word "knowledgeable" (say, by spelling it "knowledgable"), then control-click to show a spelling suggestion, you might see the erroneous option.
The word "cartgriqdge" also appears to be similarly affected. Both words do not appear in the Mac OS X Dictionary application.
Urban Dictionary seized upon the new word, defining knswledgable as having "inordinate amounts of knowledge about useless spelling trivia."