"Update your grahic driv-"
I have an up-to-date graphics card! The problem is different!

ISSUE?:
Let me say an issue that IS an issue and not the users fault or their computer. I've been chatting on the forums and many, many people have been reporting that in the recent 1.9 snapshots. (About 15w40's) the chunks have either been rendering strangely, causing holes and gaps. Or they plainly wont render at all. Mobs also seem to experience some oddities of rendering inside these holes, they can't tell whether or not to visually disappear or stay rendered, causing them to sometime flicker in and out. It's not the same problem as with the MC-62958 because with MC-62958, the chunks TILE, they duplicate and repeat and this ISN'T that issue, since the chunks themselves don't tile/repeat, they just visually disappear.

TEMPORARY WORKAROUND?:
You see the problem is that the chunks aren't showing up (Visually, the hitboxes of blocks are still visible and player interaction is still possible) , this can easily be fix by "F+A" every 80 blocks, and this is a temporary work around. Sadly if you are embarking on a long journey, you have to do A LOT of times.

WHY HAVEN"T YOU REPORT IT BEFORE?:
The reason why is because that when it comes to this kind of stuff, everyone immediately assumes it's the USERS computer, the cards are out of date. They're running on an old OS. So on so forth, and because of that, this kind of bug keeps getting marked as "INVALID" because the admins assume it's the users computer and not the game.

SO WHAT'S CAUSING IT, WHEN DID IT APPEAR?:
This kind of issue is most likely caused the "Cannot load chunks in a boat" problem, because when the new boats were released, the chunks started to visually bug out and didn't want to render. With the boats, the chunks just simply didn't load at all, similar to a chunk error. However, when the boat bug was fixed, the chunks started to render like in the screenshots below more frequently.

This most likely has to deal how the chunk culling works, and how the perspective changes. (The thing when you look away and chunks not on screen don't render, but the collision does?) This may and well be tied to the block lag issue people have been experiencing.

PEOPLE TALKING ABOUT THE ISSUE:
http://www.minecraftforum.net/forums/minecraft-discussion/recent-updates-and-snapshots/2546364-why-wont-they-fix-the-graphics-issue#c7