The first thing I would try is checking for software updates; Tools > Update Phone > Update Firmware. Also, clear the cache and cookies in Settings > More > Browser as a corrupt cache can cause various issues on the Exclaim. If that doesn't resolve the issue you may need to do a master reset on the device. Does it happen at specific time or while using a particular function of the device?
It just started happening so I deleated the four short videos I had and all my text messages and it is now freezing and saying I can not receive text messages ebcause the memory is full. I will try deleting cookies now
I ave the same issue. Mine also turnes white..but will then turn black. I am getting a call and it will be black, so I can not see who it is. I think they program the phones to act up over a certain time or do something to them, so we will have to get a new phone.
You should have the device looked at in a repair center if a master reset doesn't fix your screen issues. It's really in our best interest to make devices last as long as possible since subsidizing discounted upgrade prices carries a very high cost. Send me a private message if you would like to attempt a master reset because I will have to disclose private information about your device. (Your MSL)