Couple of hours earlier I installed the drivers of a HP DeskJet 3000, which I found here: http://hplipopensource.com/.
Since that moment I cannot install anything from the Ubuntu Software Centre. It seems that my root password is wrong now. But I haven't changed it! I have no problem log in to my profile, using my ordinary, very first password I have set when I installed Ubuntu, but when I need to use it as a root password, it is simply does not work...
Any ideas how to fix the mess?
Thank you in advance!