Does it happen from the moment you turn on the computer, or just in the OS? If it's all the time, you might have loosened a cable when you were cleaning it. You could check the cable connection on both ends (at the screen, and at the motherboard). The only other thing is you might have damaged the panel when cleaning it. Replacing a panel is extremely easy on most laptops. A dozen screws or such, and they just swap out. Usually there's two cables. One for video, and one for the backlight. Both are quick disconnects. Just remove yours, and eBay search the part number on it.
Yes, it happens from the moment I turn on the computer. Is the panel the same thing as the screen?