Yes, I experienced this flickering issue with a CrossFireX ATI 5770 X2 Catalyst version:13.1 Win7 64bit single HDMI monitor. To resolve the flickering I created a custom Catalyst 3D Application Setting and set the CrossFireX Mode value to "disabled".
That resolves the flickering but also obviously results in much lower performance. Instead of getting 70+ FPS on CrossFireX ULTRA I get about 40. Still good but would prefer the higher results.
I'm still at Catalyst version 13.1 as it seems more stable for me. Tried the beta 13.8 but was too unstable.