QBDL error Clients: There was an error adding, modifying or deleting XX because it is already in use

QBDL error Clients: There was an error adding, modifying, or deleting XXX because it is already in use

This error is cause by the item being locked in QuickBooks, most likely because it was being accessed during the QBDL sync.  Make sure no one is using QB at the time of the sync.  To ensure that a record does not remain locked, close all screens in QB and then close QB before you sync.