>With a regular combobox and SP4.

There should be no problem with it!!! There must something else.

I just retried it in a new small project without any problems. My advice now is that you build a new small project containing the necessary controls (2 forms, 1 command button, 1 combo box) and play with it. If this is not working, re-install SP4 (or install SP5 or re-install VB and SP).