Need more details. Evo?  DBA Classic?  What version?  ISTS Enhancement date?

In that version, IN-B is actually calling PO-L to do the vendor part entry.  There are some shortcomings in DBA Classic with regard to programs calling other programs.  IN-B call to PO-L should be OK but if you are in IN-B because you were in BM-A entering a component and BM-A called IN-B which in turn wants to call PO-L I have seen strange things happen.  However since you are saying this happens both when adding new or editing existing, I suspect a different culprit.  When you first load DBA and the license screen pops up with your name and address, DO NOT close that screen by clicking the "X" in the upper right corner.  Press Enter or any other key but DO NOT click the "X".  I have no idea why but that causes the programs calling other programs not to work (among some other things).