This is reproducible using beta 1 I think it is, build date July 31.
Create a new form - macros -> new form. Make it a toolwindow, borderless. Click on listbox control in the properties window, then click on the form to try and place a listbox and the following occurs.
Invalid number argument
dlgeditv.ex 13901 dlgeditv:_create_control(383,bblistbox,0,120,300,150,150) p_window_id: 383 p_object: OI_FORM p_name: xbar1
dlgeditv.ex 12124 dlgeditv:_decreate_control(1) p_window_id: 383 p_object: OI_FORM p_name: xbar1
dlgeditv.ex 10312 _ainh_dlg_edit.lbutton_down() p_window_id: 83 p_object: OI_EDITOR p_name: