Crazy Chunk deloading in 1.8+

The first thing i want to make clear: THIS IS MODDED. it genarally only happens when i mod the game. if there is a specific site for this, please let me know.

anyway, whenever i go into an open place (not in a big building like a prison server, otherwise anywhere) my chunks turn gray and sometimes flash in and out. I have an old computer too, this does not happen there.... no idea. any help? Minecraft still works though, no crash report.

This seems to happen with most mods, i've just posted and re-noticed it recently while playing pixelmon.

Oh yea, another thing, use vbos crashes my game, and my drivers are fully up-to-date. not that it changed anything when i did update them.