Error occurred in server thread; java.lang.OutOfMemoryError

I am researching intermittant problems of one of our systems missing a message now and then.  I set up an outbound SMAT file to be able to troubleshoot this.  Early this morning they were missing an A02 transaction, this transaction did not make it to the outbound SMAT file however this error was in the SMAT file around the time this transaction should have gone through:

Error occurred in server thread; nested exception is:

java.lang.OutOfMemoryError

Any ideas as to what this means and what I should do to correct this problem?

Thanks for your help!

Gina