The computer in question is a retina macbook pro 10,1.
I have a television that I normally connect to via the builtin HDMI port.
After the upgrade from Ubuntu 14.10 to Ubuntu 15.04 (and thus to the nvidia-346 driver), the television no longer recognizes the connection from the macbook when I plug in the HDMI cable (although the Display Settings app, nvidia-settings, and xrandr do (apparently correctly) see the TV).
I verified that I do see the correct behavior after downgrading to nvidia-340, and also that installing nvidia-349 (from the xorg-edgers ppa) does not remedy the issue.
ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: nvidia-346 346.59-0ubuntu1
ProcVersionSignature: Ubuntu 3.19.0-16.16-generic 3.19.3
Uname: Linux 3.19.0-16-generic x86_64
NonfreeKernelModules: nvidia wl
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Fri May 15 20:52:13 2015
InstallationDate: Installed on 2012-08-24 (994 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64+mac (20120724.2)
SourcePackage: nvidia-graphics-drivers-346
UpgradeStatus: Upgraded to vivid on 2015-04-23 (21 days ago)
mtime.conffile..etc.modprobe.d.nvidia.346.hybrid.conf: 2015-05-15T20:49:35.165098
Appears to be fixed in nvidia-352 (xorg-edgers).