Problem with using two monitors on nMP.

[iamMacPerson]

Last night I enabled FileVault of my nMP because of recent security issues here. Anyway, point being after I did so my Mac Pro started having problems with the displays. Mainly, my desktop background would change to one I haven't used in months on my primary monitor, but the one on my 2nd monitor wouldn't change. The FileVault login (which happens earlier in the process) now takes place on the 2nd monitor instead of the primary monitor. Even before FileVault, the Apple logo would show up on the 2nd monitor instead of the primary. Note that I had a similar problem with my 4,1->5,1 oMP when it was my primary machine. Any ideas as to what I can try? I have tried SMC and PRAM resets, checked the disk permissions, ran Diagnostics and tried SafeBoot to no avail. Thanks!

Primary Monitor: Dell ST2421L connected via HDMI
2nd Monitor: 20" Apple Cinema Display connected to Thunderbolt port via Mini DisplayPort to DVI adapter.

 

[ActionableMango]

Any ideas as to what I can try?

Maybe corrupted desktop picture database. I would try moving the following file to the trash, then logging out and logging in. Hopefully desktop picture changes after that point will stick.

~/Library/Application Support/Dock/desktoppicture.db

This file is safe to delete--when OS X needs that file and finds it to be missing, it will create a fresh copy populated with default settings.

 

[mjohnson1212]

On my nMP I have one monitor connected via display port and one via a display port to DVI adapter. The display port one is my primary display and when I boot it's a crap shoot where the boot screen will show up and the logon screen.

It's about 70% of the time on the primary monitor but it changed when I went to Yosemite. It was more random on Mavericks.