Disabled "me" module, Upgrading 6.22 to 7.4, Invalid text representation: 7 ERROR: invalid input syntax for integer: "

Issue Summary

Before the upgrading, I did the housekeeping thing as following:

1. Disabled all contributed modules;
2. Removed all the contributed modules folders;

Using Garland theme.

The upgrading from 6.22 to 7.4 using update.php went smoothly.

When I tried to login from /user, get Error page showing:

The website encountered an unexpected error. Please try again later.

Through PhpPGAdmin, I checked the watchlog and found the error log as the following:

PDOException SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for integer: "me": SELECT base.uid AS uid, base.name AS name, base.pass AS pass, base.mail AS mail, base.theme AS theme, base.signature AS signature, base.signature_format AS signature_format, base.created AS created, base.access AS access, base.login AS login, base.status AS status, base.timezone AS timezone, base.language AS language, base.picture AS picture, base.init AS init, base.data AS data\012FROM \012{users} base\012WHERE (base.uid IN (:db_condition_placeholder_0)) ; Array\012(\012 [:db_condition_placeholder_0] => me\012) "DrupalDefaultEntityController->load() drupal.7.4/includes/entity.inc" line

FYI, there was a module called Me Alias installed in 6.22 ( http://drupal.org/project/me ). I disabled and removed Me module before I started the upgrading.

Any clue on this issue?

The site is hosted by slicehost:

PHP 5.2.17-0.dotdeb.0
PHP memory limit 128M
PostgreSQL database 8.3.12
Unicode library PHP Mbstring Extension
Web server nginx/1.0.5