My minecraft keeps crashing in 1.7.2 after I use a World Edit command? Any reason?

Please let me have a answer As soon as possible.

It's possible that you don't have enough RAM dedicated to Minecraft. Or, you've selected too big of an area for your computer to handle. Try allocating more RAM and keeping your selections under 1500. If that still doesn't work, try re-installing World Edit on a un-modded jar file.

Best of luck!