Big black vertical bar on external screen I'm trying to plug an external screen on my 2010 macbook pro 15", but when I set the maximal resolution, 1920*1080, the image seems a little constrained, and a big black vertical bar appear on the external screen. Here is a picture of it.



When I move my cursor from my macbook to the screen, the cursor goes straight from the edge of the MBP to the visible part of my wallpaper on the external screen.

When I set up a lower resolution, the problem goes away, but the display is then a little blur, because it's not the native resolution of the external screen.

Does anyone have any idea what I can do to have a good display ?

Thanks.

Edit


I tried various frequencies with no success. 
I followed this post that seems really close to my problem: Mini DisplayPort to VGA adapter and Widescreen (FullHD) Monitor with no success. Deleting this /Library/Preferences/com.apple.windowserver.plist didn't fix the display.
This bug only appear with my MBP. Other colleague with same generation MBP have no problem to use this screen at 1920*1080. But I get this problem only with this screen and no other.
I tried to use another VGA &lt;-> MiniDisplay, same result. Tried to use a DVI &lt;-> MiniDisplay port, same result.


I'm pretty stuck on this one. Do you think I might call Apple?
My monitor shows exactly the same black sidebar on the left. Tried many tips and tricks. And finally unplug the miniDP to VGA connecter on both side and reconnect again solve the problem. 

I tried to change the VGA side here and there for hours. :( so stupid me. So I guess some other also had the same experiences but I don't know why the answer is marked down to negative scores...

I didn't mean to solve all the problem for all. But just a mark for myself that shows it solved my problem and hopefully will help some of the others.