I have a large sheet with external links and plenty of cond formatting.

I am trying to insert a row but bring all the cond formatting with it by copying an existing row, then insert.

It works for a fraction of a second - then Excel (2010) deletes the inserted row as if to say "oh no you don't" and there is no undo path. It is as if I've hit undo immediately after right clicking the row and selecting Insert Copied Cells

Any idea what is happening?

This doesn't happen with other workbooks.