OK - here is a strange one.  Using T7POA, classic view - start entering a PO, finish it, print it, it asks if you printed it correctly, click yes, that screen goes away, the PO-A screen stays there, but the PO pulldown comes up over it.  Click back in the PO-A screen to enter the next PO and when you key in the vendor, the vendor information comes up all blanks.
 
What's weird is that if you do this in the EVO view, you still get the PO pulldown popping up (minor annoyance) but when you go back into the PO-A screen, it behaves correctly (vendor info populates when you key in the vendor).  The problem only happens in the classic view.