this might be a very rare case but a user ran into the following issue:
"When a Linux user's gnome2 login keyring is corrupted or removed, all other applications (gwibber, empathy, etc.) allow the user to regenerate their login info on relaunch. Your app does not work anymore. Worse, if the user tries to start over by uninstalling, verifying the deletion of all contents in /opt/salesforce.com, and reinstalling fresh, your app appears to never work again on this machine."
After the keyring has been removed ELS calls throw an error.
Trying to reset ELS does not help.