A change to index range handling was made in 4.20 Build 3555 (20/3/2008) and 5.0 Build 3819 (prerelease) which affects applications created in prior versions that use workareas for the both lower and upper range limits with a blank value to select only records with a blank value. If either workarea is blank, that range limit is ignored, as if no workarea was supplied. To select blank records only, assign Makekey("") to the workarea. This ini key if nonzero will make the limits revert to the previous behaviour.