R – Flex ComboBox in a Datagrid loses values when I scroll horizontally

I have a very strange problem in a Flex 3.4 Datagrid. One of the columns is a ComboBox – I have my own custom renderer for the ComboBox. I use it to select my data and then make a "save" to the db. Upon return the comboBox loses its value. Even stranger is that when I scroll the datagrid area to the left (by moving scrollbar right) – the values in the ComboBox change!! When I scroll the datagrid right (by moving the scrollbar left) – the values in the ComboBox don't change.

Has anyone seen anything remotely like this in a Flex app?

Thanks

Khalid