YOUR MAC OS X STARTUP DISCK HAS NO MORE SPACE AVAILABLE FOR APPLICATION MEMORY

That means your hard drive is almost full. You need to clean it off. Most of us have some old files hanging about that should be scrapped. Other files not needed on an everyday basis can be archived to an external hard drive.

Here is a very good article on your problem and how to fix:

Freeing space on your Mac OS X startup disk

This is OS X's way of telling you that some process running on your computer has taken all of your RAM and Virtual memory. You need to use Activity Monitor to locate which process is doing it and kill it.

http://thenextweb.com/apple/2011/01/15/how-to-use-activity-monitor-to-make-your- mac-faster/

What version of Mac OSX are you running? Under the Apple menu, select "About this Mac" and you'll see your version listed.

Clinton