if you get an error saying "cannot open QB file, it already open.." error, try this simple fix: 

1) open the QBINSTANCEFINDER17.INI file (C:\ProgramData\INTUIT\QuickBooks\QBINSTANCEFINDER17.INI). 

2) clear the entries in this file and close-.YES to SAVE. QuickBooks uses the QBINSTANCEFINDER ini file to keep track of open instances. Apparently when a QBW32.exe process gets shut down abnormally, entries in this file are not always cleared as they should be. Usually that doesn't cause problems but can in certain circumstances.

3) RE START QuickBooks before trying again!!