Attempting the constraintColumns/Rows sample code from labs at:http://labs.adobe.com/wiki/index.php/Flex_3:Feature_Introductions:_Enhanced_Constraints
The code offered is <mx:ConstraintColumn id="col1" width="100" /> Tosses: >> Error Parse error at '<mx:ConstraintColumn>'. line 6 1193098009250 12 >>Warning Design mode: Error creating item mx.containers.utilityClasses.ConstraintColumn in parent Canvas. Autocomplete offers to instantiate 'mx:constraintColumns' (additional s) but compiler again tosses a parse error.
