Can't copy a block in nav tree due to Duplicate IDs err

Hello,

I am using PADS9.5 DxD Schematic Editor. I am trying to copy a block under navigation tree but got error "Can't complete the operation" and I checked my output window, there is an error message "Error 1296: Duplicate IDs dectected. Run DxD Diagnoastics to fix the problem". I ran DxD Diagnostics and saw no Internal ID duplication error. I also tried to find the explanation of the error message under the list of errors but there is no such number. Did anyone see the same problem before?

Thanks

David