The customer has several programs that all share the same Runtimes and Foxuser files. Only 1 program exhibits this behavior. What actually happens is this - when the uparrow key is pressed it appears to do the On Key Label for F10 which calls another screen. When that screen is closed, the field the cursor was originally in now has '666' in it. We have replaced the runtimes, the foxuser files and the program exe. The customer has 2 virus check program on their machine but I don't know if they are current. Right now I am scratching my head.