When I was copying some worksheets from one workbook to another, which
contains a lot of graphs. I found out that I can only copy 7 sheets with
graph, the 8th one was copied but no graph was copied over.

And if I save the workbook that I just added several sheets with graphs, I
can't reopen it within the same excel. I have to close Excel and reopen
another one to open it without causing serious error.

My question is, what exactly excel does when I was copying worksheets from
one workbook to another? Obviously it is clipboard. What else is happening?

Thanks a lot!

Jin