Exactly the same problem here, HDMI connection loses signal as soon as Windows loads (it displays fine until the Windows 7 orbs stop rotating) but VGA works fine. I can also disable and then re-enable the driver through device manager and have the HDMI usable until I reboot.
I am using Windows 7 x64 (I have tried Windows 8 x64 as well, exactly the same issue), G2020 processor and MSI B75MA-E33 motherboard.
This thread has gone a bit quiet, anyone looking into this?