Help
Why cannot i put a button on the sheet I want to?

I can do it on a blank sheet or even other sheets in the same workbook.
As far as I know there are no differences with the two sheets.
The forms toolbar cursor changes to a small thin cross on both sheets but will not generate a box on the sheet I want to put it on.
Is there perhaps a setting I need to adjust??
cheers
nobby

PS its the same with the crawing toolbar, cannot input text box or callouts etc?????
PPS also cannot edit the size of a comment box.

Must be a setting somewhere I clicked.