It could be that the video settings reverted back when you switched from external display (TV) back to the computer monitor.
If you're using a different HDMI input than the one before, try changing the name of the input from "----" to "PC".
I have the 6000 series 40" LED TV hooked up to my PC via a DVI to HDMI cable and everything was fine until recently I unplugged the tv from the video card.
After I reconnect the TV, the picture won't fit on my entire screen anymore, and as I recall I just need the just scan function to make display area to fit the entire TV... NOT! and changing picture modes from 16:9 to Screen Fit just wouldn't help!
resolution is set to native TV resolution but no matter what I do, there is still black boarder around the entire picture.