debug log:

Login Manager: observer notified for form submission.
Login Manager: Checking if logins to http://conkeror.org can be saved.
PwMgr mozStorage: Getting login saving is enabled for http://conkeror.org
Login Manager: Searching for logins matching host: http://conkeror.org, formSubmitURL:
http://conkeror.org, httpRealm: null
PwMgr mozStorage: _searchLogins: returning 0 logins
PwMgr mozStorage: _findLogins: returning 0 logins
Pwmgr Prompter: ===== initialized =====
Pwmgr Prompter: Notification bars not available on window
Login Manager: Caught error in onFormSubmit: [Exception... "Component returned failure code: 0x80004005
(NS_ERROR_FAILURE) [nsIStringBundle.formatStringFromName]"  nsresult: "0x80004005 (NS_ERROR_FAILURE)" 
location: "JS frame ::
file:///nix/store/043pc7lv8nz1zyvghcg4pkra2c35qf0m-xulrunner-2.0.1/lib/xulrunner-2.0.1/components/nsLoginManagerPrompter.js
:: <TOP_LEVEL> :: line 1338"  data: no]
Login Manager: onStateChange accepted: req = http://conkeror.org/FrontPage, flags = 0x30004
Login Manager: domEventListener: got event DOMContentLoaded
Login Manager: Counting logins matching host: http://conkeror.org, formSubmitURL: , httpRealm: null
PwMgr mozStorage: _countLogins: counted logins: 0