I have an ASUS M4A88TD-V EVO/USB3 motherboard with an AMD Phenom II X4 965 3.4GHz CPU, 8GB RAM, onboard Radeon HD4250 GPU (driving an LG IPS 224 display) and a graphics card with Radeon HD 5770 GPU and dual DVI/HDMI outputs (each output driving a Samsung Syncmaster B2430 display).
I was running Catalyst 11.2 and all three displays were working fine. I decided to update to Catalyst 13.4 and after the BSOD (no warning to uninstall 11.2 before updating) managed to get the two displays on the HD5770 working OK. The other screen on the HD4250 is however receiving no signals and doesn't appear under the Catalyst 'Desktop Management' tab.
Under the 'Information' tab, both the HD5770 and the HD4250 are listed with what look like OK values in all the fields.
Any ideas why the third display on the mobo's HD4250 has suddenly stopped working and how I can get it back will be most gratefully received.
BTW - If you're wondering why I went so long on Catalyst 11.2 before updating, I had a horrendous time a few years ago when I updated to 11.2 and was only persuaded to update today as I'm about to install some software (Sony Vegas Platinum Suite 12) that requires at least version 11.7 to function...