The error "Duplicate PUBLIC name CMEMOOBJECT in USE module CoreEmailClasses" can be fgiven when open a document in mail or in other databases. It is caused by caching problems or by lotuscript compiling going a bit wrong.

My solution is to first do a Tools->Recompile All LotusScript in the designer on the template or database.

Replace the design if it was a template. Make a backup of the design if you are not sure - safety first

Get the user to close down Notes or at least close database and do a F5 and relogin in.

If the problem continues Compact the Workspace, close Notes and try deleting the CACHE.NDK in the Notes Data directory and restart Notes.