Well using WT.setLocaleToCurrent solved the uppercase problem but it introduced a new problem
After invoking WT.setLocaleToCurrent() using Ä or ä in IUIContent.enterText() will enter an A or a in the field. So Ä and ä loses their umlaut (http://en.wikipedia.org/wiki/Umlaut
). Ö,ö,Å and å works as expected when using WT.setLocaleToCurrent.