Thanks Colin for your reply
I will attempt to reconstruct a series of steps next time it happens. If it is a rare occurrence, then I am a rare bird indeed because I have experienced in 5 or 6 times in the past 2 weeks. Each time the DE was open along with several other objects such as forms, progs, tables other reports. I have also noticed that it tends to occur when I copy objects from another report into the offending report. That could be a result however of other objects being open simultaneously

Vince