word 03 Crashing. Lost file

XP Pro
Have a user working on file(s) that he created with word 2003. Sometimes word will lock up and crash displaying an error message “word cannot open the file” then gives 3 generic reasons, one was that the system did not have enough memory (pc has 2 GB).
When the user goes to open the file again, the file is gone.
The Word files are being saved on the network
Any ideas?