skamp: Sorry but what & where is vignette,I cannot see it in my options.
In the Options for the launcher, check "Show Advanced Options". One of the options about half-way is vignette, turn it to disabled. I don't know if this is actually what is your problem though, since it should have been on before anyways.
That's what vignette does. It's just a black border around the edge of the screen. Artistic design, if you will.