I was getting the same error when doing the one click update: http://imageshack.us/photo/my-images/545/errorce.png/
But even though error occurred during update, there were some changes. There was a new link "Database" showing up that was not in 1.7.3. And at the bottom, the footer area, the Joomla version number disappeared. It was not showing 1.7.3 nor 2.5.1.
At the same time, the "Quick Icons" on admin home were showing old 1.7.3 icons... with the "Joomla is up-to-date" icon missing.
==========================================Doing these did not fix the issues:
* Deleting sql files in: administrator/components/com_admin/sql/updates/mysql and trying the whole update thing again with clean Akeeba backup restore.
* Deleting joomla.xml from site's root and re-doing the whole process.
* Fixing the database from new "Database" link returned that database issues were fixed, but the site was still not showing version number at footer (in admin area), and also, the "Quick Icons" were still old 1.7.3.
Look at this in "Database":http://imageshack.us/photo/my-images/163/error2j.png/
It says "Database schema version (in #__schemas): 1.6.0-2011-01-10"
That means it is I who did some upgrade before that was not done properly, and the database schema was not altered. Somehow it did not generate any error when I upgraded to 1.7.3 from and earlier version. But now, going to 2.5.1, the problem came to surface.
And these are all the errors:http://imageshack.us/photo/my-images/209/error3.png/
All these will be fixed when I run the sql files from: administrator/components/com_admin/sql/updates/mysql
==========================================Doing these fixed the issue, and site was updated successfully using one click update:
* Did a fresh 1.7.3 install
* Downloaded all the sql to local machine, from here: administrator/components/com_admin/sql/updates/mysqlhttp://imageshack.us/photo/my-images/338/sqlfiles.png/
* Restored my site's backup using Akeeba
* Using phpMyAdmin, opened my site's database, and started running the sql scripts one-by-one starting with the 1.7.0-2011-06-06-2.sql, which had these queries inside for example:
ALTER TABLE `#__languages` ADD COLUMN `ordering` int(11) NOT NULL default 0 AFTER `published`;
ALTER TABLE `#__languages` ADD INDEX `idx_ordering` (`ordering`);
So ran all the sql scripts one by one that were downloaded from: administrator/components/com_admin/sql/updates/mysql
* Then, look at this:http://imageshack.us/photo/my-images/252/700p.png/
This is what the 'schemas' table contained in my fresh 1.7.3 install. But after restoring my site's Akeeba 1.7.3 backup, this table was empty.
* So next I ran this:
INSERT INTO `rgs_schemas` (`extension_id`, `version_id`) VALUES
* Then I went to one click update and tried the update, and it was done without any errors:http://imageshack.us/photo/my-images/812/successful.png/