Thanks for your suggestion. Actually I did step through the code. But I did not find anything that clears the form. After the class is run, I see form's unload event being fired (I have a line of code in there). But the form stays there until the class is completely executed, so it is even harder to identify the offending code. I have CLEAR myotherclassname command, but nothing that should affect a form level object.
Solutions: when you want it, as you want it!