protecting data validation??

Can I protect a shared sheet from any changes being made to the data validation by password?

Not sure exactly what you are looking for here. If you mean you want someone to enter a password in order to make a data validation selection, then no, not really, you need to unprotect the sheet in advance of making any alterations to a protected sheet.

If you mean to protect data validation from accidental or "purposeful" delete validation rules or "override" them by copying and pasting, then you would need a VBA function like this one: http://spreadsheetpage.com/index.php/tip/ensuring_that_data_validation_is_not_deleted/