How do I repair the White Screen instead of normal boot up?

I have a 2008 iMac running Yosemite 10.10.5. It suddenly stopped booting, instead it only shows a white screen. I can boot it into safe mode and I ran "disk repair" and "disk permission repair" off of the disk utility. It still does not boot. Anybody have any suggestions on how to repair this so it will boot and work again? Thanks for the help!