Steve, I've been trying but can't duplicate your problem so far, although I think I've seen it happen once or twice here.
Did you try a restart of the Lookup proogram? Or restarting DM780 then restart Lookup? Restarting Lookup or both usually clears things like this.
Are both computers running the same HRD version???
Can you repeat the problem on the same computer?
I don't think there's any setting that would cause this.
Ed - W4ELP