As said in the doc ( http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/mx/controls/ToolTip.htm l ) Tooltips (and errorTips) dont have a mobile skin... You could create your own skin or create your own componant... The errorTip componant is pretty basic and a custom copy could be done without too much effort imo...
Solution was a little diffirent.
To achive the old mx error tooltips, we have to override the default FormItemSkin.mxml and modify it:
1. Remove the errorTextDisplay component
2. Set contentGroup showErrorTip to true
How do we override the default FormItemSkin? I have a form with little room for eror messages and the errorTip messages would solve the problem.
Thanks man, solved me a lot of trouble, the default skin is simply too ugly to be used.