The state legislature overrode the Governor's veto. The vote was 28-14 in the state assembly, and 14-7 in the state senate, exactly the amounts needed in each house.
The governor had argued that a 2002 state constitutional amendment banning gay marriage precluded the partnership bill. While I haven't seen the text of the Nevada bill, it apparently grants same-sex (and opposite-sex) couples substantially all of the rights and protections of marriage when they register as domestic partners. By my count, Nevada was one of nine states that amended its constitution to ban only same-sex "marriage" and not also "similar" unions. Three of those nine states (California, Oregon, and Nevada) now have broad domestic partnership laws.