Even though this topic was discussed already quite some time ago, I would like to add the following.

According to the discussion here [url=http://www.lightcrafts.com/forums/showthread.php?897-Unable-to-save-preferences-%28file-lock%29]http://www.lightcrafts.com/forums/showthread.php?897-Unable-to-save-preferences-%28file-lock%29[/url] the problem can be related to the home directory being mounted via NFS.