I doubt that rebooting the camera will help.... But it's free to try.
Rebooting resets everything in the camera and there are two ways to do it.
1. Turn off the camera and remove all the batteries, both the main and the little memory batt (the silver memory battery is on the LH side of 5DII, under the USB and other miniports, partially hidden by the rubber cover... you need a precision screwdriver to remove the battery).
2. Turn on the camera and let it sit turned on for a minimum of half an hour, but it might take over an hour. This allows remaining charge in the camera to drain off.
3. Turn off the camera, reinstall the batteries.
4. Turn on the camera and check the date/time. You should need to reset it. If not, try again.
Alternative, faster method:
1. Turn off the camera and remove all the batteries, both the main rechargeable and the little memory batt.
2. Turn on the camera and press the shutter release button once. The camera won't fire, but this should immediately drain all remaining power in the camera's circuitry.
3. Turn off the camera, reinstall the batteries.
4. Turn on the camera and check the date/time. You should need to reset it. If not, try again.
But I really doubt rebooting the camera will make any difference. If the camera is new, Canon might replace the LCD under warranty. I don't know what their tolerances are for dead/stuck pixels on the LCD monitor screen... might not be bad enough to fall under warranty repair. It's really just a nuisance, anyway, doesn't effect anything important. Though I can understand why someone would be upset after spending $2000+ on a new camera!