Need more details to solve problem. To get more details (which line cause error, why and s.o.), run EXE in development mode as described in next paragraph. In addition, define error handler at start of application running using 'ON ERROR' command, that will show more information about error in the message box, like line number of code where error occurred, procedure name etc. Look to VFP help on this command for more details and samples.
Compile EXE with debug information (right click on project manajer, Project Info, check 'Debug Info' checkbox on first page). Than run compiled EXE application in development mode: "DO MyApp.exe". You will be able to debug errors using 'suspend' button in error message box, that appear oly in development mode. With error handler use 'SET STEP ON' command when error occurred to debug lines where error occurred.