Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here
What should happen is that blocks should be visible non-flashing blocks.
What actually happened was...:
Describe what happened here
mainly on severs my vision will go crazy and begin flashing show only dots and lines in the place of blocks and white squares in the place of most items in the inventory. It also seems to cause crashes and lag-outs. I'm not sure what is causing it. Please help if you can. Thanks.
Steps to Reproduce:
1. I don't know how it starts but please help if you can. thanks
2. It also seems that I can't take acurate pictures when it happens
3. ...