Hello,
the problem is, there was a bug in versions prior to 1.4.2 causing that the upgrade capability does not work with PHP4, which is probably also your case. (it however works fine with PHP5)
We are sorry for this.
To update to 1.4.2, you have 2 possibilities now:
Possibility I (remove and add):
1. use the backup utility to store your "custom redirections" or backup the whole DB table (jos_redirection is the default table name) using phpMyAdmin or similar utility;
2. Uninstall JoomSEF using the Joomla! build-in installer and install the new 1.4.2 package
3. renew your custom redirections from backup or renew the DB table
Possibility II (manually update):
1. download the new 1.4.2 package to your server and unpack to any directory
2. rewrite the file administrator/componets/com_sef/installer/update.php
-- after this, the autoupdate should start to work, so you can now use it
-- or rewrite all the other files in components/com_sef and administration/components/com_sef manually also
The possibility II. should not touch your existing data or configuration.
For further details, check documentation, where the manual update process is also briefly described.
After fixing the update.php files or installing 1.4.2, the next on-line updates should work fine.
Best regards,
ARTIO Support Team