UPDATE: BEFORE YOU VOTE, PUT THIS APP ON YOUR PHONE! The Voter Fraud Mobile app for iPhone, iPod Touch and iPad: you may not have to use it, but you'll be glad if you do.
In North Carolina as well as in Nevada, voters trying to vote straight-party tickets on machines have reported problems with the ballots being "defaulted" to some previously-set parameter --in other words, the ballots were pre-set to vote for "the other guy."
I have already voted and I noticed no such irregularity on my ballot. But be aware that This Sort Of Thing can (and does) happen. Be diligent when casting your vote: make sure your final ballot is the one you selected. Remember that in many states (including mine), going down-ticket to vote in races where your party runs no candidate will invalidate your straight-party vote at the top of the ballot.
Of course, the simplest and best (if not shortest) solution is not to vote the straight-party option at the top of your ballot, but to vote separately in each individual race.
But whatever else you do, do go vote. Display Your Civitas!