ArgoUML says:"...ran out of memory..."

  This is a strange thing,although I have resolved it,but I haven't understood it yet.About a week ago,when I run ArgoUML,it said "ran out of memory,rerun argouml with heap size increased." regularly.Then I did a lot of things:scan viruses,update jdk to 1.5,reinstall OS...,but it is no effection!

  Later,I searched a mail at argouml.tigris.org,resolved this matter by adding Non-Standard Options with "java" command.it is:java -Xmx192m -Xms192m  -Xss8m -jar argouml.jar.

  There are still two doubts in my mind:

  1.Why did I run the argouml normally before a week ago but can't run it normally later?

  2.Does argouml on earth need so large memory to run it?I have a lot of doubts!