Has this problem been figured out? I'm having the same problem and would like to figure out if there is a solution.
I'm trying to run dual monitors extended.
1. Samsung SyncMaster 2333HD (HDMI in, DVI in, VGA in)
2. Planar PQ1910M (DVI in, VGA in)
My video card is an ATI Radeon HD5450 (1 HDMI out, 1 DVI out)
My computer power settings are set to put the monitors in standby after 15 minutes idle. The computer does cut the signal after 15 minutes and the Planar goes into standby (DVI-D) but the Samsung (HDMI) displays a 'no signal' message that floats around the screen. (The Samsung setting is HDMI-PC) I unhooked the Planar and connected the Samsung by DVI-D and the monitor does go into standby. Since the problem was HDMI related I decided to try and split the DVI output to both monitors. I then hooked up a DVI to DVI-D & VGA splitter, using the DVI-D with Samsung. However, extended mode did not work with that setup. I figured the video card was not capable of sending a digital and analog signal through the 1 output. I then got a DVI to DVI-D & DVI-D splitter and ran both monitors over the digital signal but extended mode did not work this way either. Strangly the computer still recognized the 2nd monitor as 'Secondary monitor VGA' (as it did with the VGA cable) even though it was hooked up through DVI. This is where I'm at now. I have an HDMI to DVI-D converter in the mail and I'm going to try the HDMI signal through the DVI input. If this works, I blame Samsung for not recognizing the HDMI code for standby. If it doesn't work I have to think it's the graphics card, which I really hope it's not.