iMac 27" Second Monitor Delay

[jimleszczynski]

I am operating a 27" iMac i5 2.66, 4GB RAM, ATI Radeon HP 4850 (512MB).

I have a second monitor plugged into the iMac. It is a LG 13" Flastron wide external monitor. Everything works perfectly.

However, I notice a lag when playing video games or watching netflix movies streaming over the internet.

Any ideas on what I can do to fix this? Is it fixable? Insight?