Debian won`t take the root password but did before / Can anyone post a solution ?

This is a odd one...Debian all of a sudden wont take the root password i set when i installed it but has always done so before, even after entering several times and i`m sure it`s the right one as i never changed it. AnyWay to correct this with out a complete re-install ?
I found this out when i tried to install a package & tried to enter root without any package install.