UT3 locking up at beginning and in middle of maps?

Any ideas what could be causing it? My system barely runs UT3 to begin with and it's locking up on custom maps CTF-Eurus and WAR-Tropico. Could it have something to do with free space on the partition down to 2.13GB? I'm not moving or uninstalling anything to free up space, so I may not be able to play it for about a month (new system build will happen next month). Any ideas?
__________________________