So, I'm hearing that others are having a problem, so I'll add my voice to the crowd.

I haven't noticed it outside of games, but in game my screen will flash quickly (like I hit alt-tab twice). I'm not sure what the screen flashes to, it has a bunch of circles. But it happens every 10-20 seconds or so.

this issue has been noted by a Senior Wrenchman and hopefully riot will know about it soon too if you wanna keep updated http://na.leagueoflegends.com/board/...creen+flashing thats the main post for the issue at the moment

SOLUTION TO SCREEN TEARING/ FLICKERING OVER ALL POOR QUALITY SINCE LAST PATCH REVEALED

Go to AMD website and update driver for your video card.
I just updated to beta driver 12.11 and it immediately fixed the problem.
This may have been caused by riot updating graphics but as far as myself and my friends who only run AMD.

I personally found that updating to beta driver 12.11 fixed the screen tearing.

I am running Radeon HD over clocked 7850 by Saphire Dual X. Windows 7 32 bit.

Here is the link to the driver.
http://support.amd.com/us/gpudownloa...w_vista32.aspx

Latest Beta Driver 182 MB 12.11 Beta 12/3/2012 Download
Description:
Download our latest beta driver and get a preview of what we're currently working on.
Note! This driver is provided "AS IS" and under the terms and conditions of the End User License Agreement provided therewithin.
Please note that the Catalyst Control Center component of the AMD Catalyst 12.9 Beta requires .NET 4.0 support.

I hope this helps!

I can confirm that this appears to be the solution

The beta driver seems to fix it for some but not for others (I'm among those unfortunate few). Try your luck. If it doesn't work, add your voice to the thread given by Taboss.