[AS3 / DataGrid / CellRenderer / PHP] Parameter Child must be non-null

I’m currently developing an application using Flash AS3 CS5 embedded in a PHP script and I’m having issues with DataGrid custom CellRenderer.
This part of the application has to display some information retreived from a MySql Database. Using the default DataGrid all information is properly placed in its rows/columns.
When I try to align some column fields (right, for instance) I receive an error message saying “Parameter Child must be non-null”. Well, this is driving me crazy because if I replace the data retrieved from the Database by a hardcoded array in the .fla so I can run it in my Flash StandAlone, it runs ok.
Furthermore, when I test it online using the same hardcoded data from the .swf embedded in the PHP script, i receive the mentioned error about Parameter Child.
The application (embedded in the PHP script) uses a main .swf file where many other .swf files are being loaded by User request. In some forums I have visited recommended adding a DataGrid component to the main .swf - so I dd but nothing changed.
Does anybody can enlighten me to the solution to this issue? I really appreciate your interest and contribution.