Unfortunately downgrading doesn't solve my problem. If I downgrade the driver I can enable the HDMI output, but I can't save the configuration to xorg.conf (nvidia-settings segfaults). With the 1.73 driver that is necessary since maximizing screens or using full screen applications doesn't work well (they use both monitors) unless you save and restart X.
The 1.77 driver also can't save to xorg.conf, but at least maximizing and fullscreen work immediately after applying the settings. So until this is fixed I'm afraid I will have to reboot to windows to use the HDMI output of my laptop
. Any help on how to get HDMI working with 1.77 would be greatly appreciated.