I think, I'm getting mad.....

I have a datagrid consisting of several derived columns (comboboxes). That comboboxes are filled by a dataset. They all have an empty entry and are editable.

If I can see the whole datagrid, everything works fine. If I have to scroll from left to right the value entered in a combobox not been visible before scrolling is forgotten. But only if I enter something. If I select an entry of the combobox everything works just like expected.

Any idea???