I'm searching for a solution to the same problem.
-Dell Optiplex 3010
-Core i5 3470
-HD 2500 Graphics
-HDMI and VGA output
-HDMI to DVI adapter (tried Dell's and others)
-Viewsonic VX2235 and HP L1955 monitors
-Intel 10.18.10.3621 5/17/2014 driver (also tried Dell's latest)
Notes for Dell's latest BIOS update do not mention this as being addressed, so I would like to hold off on updating BIOS unnecessarily.
I've tried changing and saving the settings in the Intel graphics control panel. The "Multiple Monitors" option only appears after the above work-around.
Above work-around works, but system reverts after log-off, sleep, or re-boot. Running a script is not an option.
Any help would be much appreciated.