Go to your device manager and tell us what version of drivers you have installed for your display device. Also knowing which graphics card you have will help if you're outputting from there. If you're outputting from the mobo directly then you need to check the onboard graphics driver from your cpu.
This probably won't do anything but, you can try using another cable (dvi instead of hdmi or vice versa) or plugging in to a different port on your tv if there is one availalbe. Might just be the cable you're using on the port but I highly doubt it cause you are getting an image...