A couple of times a day, my Solidworks (2004) will shut down in the middle of a process and return an "unhandle error" fault. What does this mean? Is the anything I can do to prevent this (and losing work)?
It means that something caused SW to Shut down. The error is vague, but the reason it shut down is broad. The one thing that I have found that causes most Unhandled errors is not cleaning out your TEMP folder faq559-884 or your out of HDD space. Your Network could be part of the issue or it could be a Video driver. If your not using a certified Video Card with a certifed Driver, that could most likely cause it to crash.
Check out "Trouble Shooting a Crash prone System" -
It also seems if you go to "fast" for SolidWorks (clicking on another function before the one being processed is finished) this will also cause an unhandled error.