Not enough storage is available to process this command

I've noticed this error pops up when i increase video settings. I've GTX 750 Ti, i5 and I'm able to play newer games (such as GTA V...) on high settings but I can't WoW?
I'll take a SS when it pops up again.
I've been searching for an answer but solutions such as recreating cache, wtf and interface doesn't work..

Edit: https://imgur.com/dZ8ZvNV

You need to allow it to run off more RAM.
Wrath is only meant to be run off 2GB of RAM max, you could disable some addons, since these are the main cause of RAM usage.

There was a file command to allow it more access to RAM but i can't remember it off the top of my head

I don't have any addons. :/