extendedData getting lost in custom node type

Carsten_Erker_(PDVErker_(Delete)_2309625)

My custom node type uses the dtree.extendedData column to store some text when creating/editing the node via an HTML text field.There is no problem until the Info->General page is updated (i.e. name or description changed): After that the extendedData is suddenly lost.Any ideas why or how to solve this problem?Thanks,Carsten Erker