Hmm Latency usually suggests a network connection issue. Maybe also a WOW player. Are you connecting wirelessly and are you now farther away from your connection. Now if you getting lag it could be from using a odd resolution.
yes, a wow player. I switched it to the recomeneded video settings of 1280x720 and still no change, the computer has never been moved since i got it, and this has never happened since i started using the tv as a monitor.
http://forums.whirlpool.net.au/archive/874429 Talks about WoW Latency. Its odd it would start to get latency from your TV. Now maybe lower Frames per second but the Latency is network related. If you move back to your old monitor now, does your latency improve. You can also have wow load optimal settings and see if it adjusts it to the proper sizing and you can always adjust the details after that.
Im just pitching in here as im no expert on the subject but what was teh refresh rate on the Monitor you used before ? Im pretty sure the TV will be running at a very low refresh and i beleive this could add latency.
I could be wrong as i said im noo expert but just thought i would mention it as a posibility.
Try changing your Catalyst HDTV setting to 720p to see if your performance improves. You are pumping a lot of data and putting a heavy load on your GPU (assume you are using HDMI sound as well) at 1080p.
What you are experiencing is called input lag which is basically the delay between when you do an action with your keyboard / mouse and when it occurs on the screen.
If gaming on a 120Hz or 240Hz HDTV then it is always best to choose "Gaming Mode". If it does not have "Gaming Mode", then manually switch the HDTV to operate in 60Hz mode. This should decrease the amount of input lag.