Minecraft chunk not loading?

I can't get this one world to work anymore as several chunks do not load (i'm standing right next to it).
I'm now underground and I can see the moon and the rest om my stairs up to the surface, but a chunk in between is missing.

I've unedMCedit and some other PGMS and cleaned up my PC to be sure but nothing is working. If I start doing things it will just put me back to where I logged in after a while. Also if I for example cut rocks they just reapeaar right away or after some time.

Anyone have other ways to handle this?

Your problem is where it says "allocated memory" its at 100% you can either save and restart your PC everytime it hits 100% or give minecraft more ram.