SpellAsYouType corrects the wrong word.  Try this in the demo page:  http://www.karamasoft.com/Samples.aspx?component=UltimateSpell

1) Clear out the textbox
2) Enter (without quotes) "This is badx" in the textbox and hit the tab key several times
3) Right click on "badx" and select any word from dropdown
4) Instead of replacing the mispelled word, the control replaces the first word!