Citrix Typing vowels and strange characters

I remember this problem on Metaframe XP and oddly enough had a call for it this week on XenApp 4.5 (though the problem is client related not citrix related)

When a user locks their screen with the key combination CTRL + ALTgr + DEL , on unlock the normal keys characters are not available and only some letters and numbers can be typed. It seems the vowels can be typed oddly enough.

Users should not use this key combination and should use the correct Lock key of
Windows Logo + L
Ctrl + Alt + Del

This will prevent the issue.