Just this morning my Dell U2412M monitor is experiencing an issue where it initially seems to have a large "shadow spot" on the right side. The display is almost completly darkened and there are small areas of brightness. I have attached a picture to hopefully help to demonstrate this:

I should also mention that it will partially go away when the monitor is turned off, but will come back after a couple of mins when turned on.
My question is, has anyone experienced this issue before and do they happen to know any quick fixes? Any idea what would cause this?
Also, I can't seem to find information about Dell's standard monitor warranty. This monitor doesn't have a service tag so I can't use their online checker.
Thanks,