Tree is not displayed when starting dynpro with Coordinates

Hello all,

I have the following problem:

A tree (CL_GUI_COLUMN_TREE) is defined and sucessfully filled. The dynpro where i display the tree has a custom control with a well defined container. Everything works, the tree is displayed on the dynpro.

When i now start the dynpro by giving coordinates

<b> call screen xxxx starting at ....</b>

<b> ending at ....</b>

the screen will appear empty, nothing is displayed.

After changing the code to

<b>call screen xxxx.</b>

everything works fine again.

Has anybody an idea what is wrong? Are there any restrictions?

thanks in advance

Stefan