YUVRAJ, thank you for the suggestion. I did update Air and restarted, but it didn't help. However, I have noticed one more mysterious symptom. When I select the Combine Files function, although the Dialog Box does not come up, a small object does appear on the screen : a vertical bright line one pixel wide and about a centimeter tall. This appears to be an artifact that is appearing instead of the dialog box. Any ideas why the real box is not displaying?