ViewSonic Monitor Not Showing on Boot

We have 2 ViewSonic VG2227WM monitors (1920 x 1080) used as extended displays on our Mac Pro. A suspected issue with the graphics card (ATY Radeon X 1900) is causing the monitor without the task bar not to show up on boot. You have to switch the resolution to something other than what it's set at for it to be recognized. (display icon at top right, under "Display 2"). To get around this until we can replace the graphics card is to duplicate a 1920 x 1080 display setting for Display 2...then just switch from one to another to force the Mac to see the second monitor.