RHEL 6.6 won't boot with dual monitors

I have RHEL 6.6 installed on a HP Elitedesk 800 G1 Tower PC which has two monitors, one connected via display port and one connected via VGA. It gets past the POST and I see the GRUB 5 second countdown, but nothing else. It just stops there. If I unplug the VGA connection, it boots up fine, then I can plug the VGA back in and manually reconfigure my displays.

I checked the BIOS to see if there are any options which might affect this behavior but saw nothing helpful.

Any idea what's causing it to hang with the VGA connected?