maybe i've too quickly blame that newest package: before upgrading it ip was resolved normally, then after upgraded ubuntu13 i've got "cant resolve url" error, so i've downgraded to ubuntu12 and the issue was solved. That why i've posted the comment #22 above. So now i'm using ubuntu12 but also get hardtime to resolving url after a cold boot: need to reload several times a page into firefox to get it (first still get "cant resolve url" error).
So i might have some borked settings with this pc. Sorry for the noise.