I have experienced this before and had to debug the way Cardyin explains. 
I found it was the form load statement to be the culprit. Try this for 
giggles. It worked for me. Unload the calling form first. Then load the 
other form. I know this sounds stupid but it fixed it for me. I don't know 
why but it did. I can show u what I had to do. This is not the best 
solution because the user sees the desktop for a split second but I 
couldn't figure anything else out. 

HTH

If ErrorCode <> -1 And Trim(UCase(CountryMade)) = "PHILIPPINES" _
          Or UCase(CountryMade) = "MADE IN PHILIPPINES" And Not gblnInOpticalVillage Then
               frmScanItemNr.Show vbModal 'get the part number
                Unload frmScanItemNr
                Set frmScanItemNr = Nothing 'clean up from form unload
               frmProdNrLotNrScan.Show
               Unload FrmCustProd
               Set FrmCustProd = Nothing
          End if