Vicky,
Go to the Sheet that you can't delete and check under Protection menu to see
if there is an "Unprotect" option. If there is, then your sheet got
protected by accident and you need to Unprotect it.
Since this option allows Password protection (you can leave it blank when
protecting against accidental deletion), let's hope an accidental Password
wasn't also entered, otherwise, you will have to copy everything to a new
document.
Ray
