java.lang.OutOfMemoryError: Java heap space

Has anyone gotten this error before? I'm trying to understand what it means and what i can do to avoid it. i"m new to matlab and i've been copying and pasting some moderately large (200x200) matrix from excel directly into the matlab command line as a way of quickly importing data.
I received the java... error after attempting to paste a matrix into matlab. i've have previously imported the same sized matrix repeatedly, so it's not clear why it suddenly stopped working. It seems as though i've got some pretty serious memory issues because, now when i try to use xlsread, i get this error, 'Warning: Could not start Excel server for import, 'basic' mode will be used. Refer to HELP
XLSREAD for more information. '
It seems as though this problem might be due to some sort of memory leak problem rather that a limitation on the amount of memory i have devoted to java since these are fairly simple operations i'm attempting that are either crashing matlab or not going through. I have been copying and pasting hundreds of time throughout the day though, so i wonder if that process is somehow gumming up the works....
I've tried restarting matlab and my computer. I repaired disk permissions. Nothing seems to fix this problem.