João,

>Hi have the DataSession to default. Any other guess.

If your two forms are set up the way you say then the datasession is there. You may need to 'activate' it by placing a SELECT statement for the main table in your Load() or Init() event.

I've found that making one of the tables 'active' in that way makes everything wake up and start acting like it is supposed to.

There is one catch, though. Say you have three forms that start out, the first starts the second, and the second starts the third. The third form in the chain won't be able to inherit the private datasession of the first.