White screen prevents access after upgrade

After the install of the

10.10.3 Update

when I restart a white screen appears and you can hear the username box and password box are there but can't be seen. I am on an 2010 summer iMac 27 with 12 gigabytes of memory and 222.9 gigabytes of room the hard drive. I have been unable to recover using the recovery HD from the previous upgrade. I will try to get a crash report and send it. When I open the hard drive with my backdrive I can open the the disk for the primary and everything is there. So the white screen seems to problem seems related to just the start up screen. I have tried everything anyone has suggested but I always get stuck on that white screen.

10.10.3 Update seems to have affected some hardware at

Now Safari has a split right screen but everything runs off the page inot infinity.