If you wan't to update XAMS from a previous version you have to apply the patch(es) from the corresponding directory. There are no patches for versions prior 0.0.5, so you have to check differences (database-specific) by yourself - simply compare the xams.sql / xams-structure.sql files...
You may want to execute 'touch /your-xams-gui-dir/maintenance' and XAMS will show a maintenance-message instead of the login-screen. But don't forget to delete the file after updating :-)