HELP! in PSP7

So I was making a nice little Underoath banner and I go to add some brushes when all of a sudden, a pop-up error box pops up when the brushes are loaded 54% and it says "Out Of Memory". How can PSP run out of memory all of a sudden? It worked perfectly last night when I was making some icons. I downloaded a few fonts this afternoon--could that have affected it in any way? I tried restarting the computer, but no luck. If it makes a difference, I have a Windows XP computer.

Thanks in advance!