Copy and move to end error message - cannot move worksheet

I have be bringing forward my previous weeks spreadsheet by copying and
moving to end with success in Excell 2003 for years. When I do the same
actions in 2007: I always end up with an error messages like: the name you
entered is not valid, then, name allready exists : Excel _BultiIn_Print
_Area_11 (or similar). Then I get a "name conflict " box which won't close.
Oh, by the way, the name I am trying to use is: Aug 5-12. Not too exotic, is
it? Can someone help is