got another HDMI cable?
I know I had blanking issues but the hdmi_boost option resolved it completely, might try hdmi_safe=1, here are all the config.txt options and more info: http://elinux.org/RPiconfig
I know I had blanking issues but the hdmi_boost option resolved it completely, might try hdmi_safe=1, here are all the config.txt options and more info: http://elinux.org/RPiconfig