The 285.38 drivers are BETA, so it can be expected that some issues may be encountered. I would report your issue to NVIDIA so the developers are aware of it and can possibly work on a fix. They may even be able to offer some suggestions to help you resolve the issue, but I would guess the odds of that are minimal. In the meantime, I'd rollback to the stock driver and wait for a driver update.
You might also attempt a clean reinstall of the 285.38 driver to eliminate any possibility of a bad driver installation - uninstall it, reboot, sweep for NVIDIA driver files, reinstall 285.38, reboot.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT