I got the same problem. After installation in Ubuntu 13.10 ,username is blank in database. Whereas the setup folder do not remove if we check the check box at last screen of installation. I rename the ht.access file to .htaccess then it was able to remove setup directory.
The ubuntu 13.10 has Apache 2.4 which has new Override parameters hence I used the given below code in apache
<VirtualHost modx:80>
ServerAdmin webmaster@localhost
DocumentRoot /var/www/modx
<Directory /var/www/modx>
Options Indexes FollowSymLinks MultiViews
AllowOverride All
Require all granted
</Directory>
</VirtualHost>
I tried to update username in database where it was blank but issue is still same.
mysql> select * from modx_users \G;
*************************** 1. row ***************************
id: 1
username:
password: sTjeTieCfj5EhM7EaANhmTrxJnS/fzMhmByf6/sA7tY=
cachepwd:
class_key: modUser
active: 1
remote_key: NULL
remote_data: NULL
hash_class: hashing.modPBKDF2
salt: a8a6f756dbf0a36ef330ee6a69ee44d6
primary_group: 1
session_stale: NULL
sudo: 1
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> UPDATE modx_users set username='admin' where id=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql>
I checked in logs (Apache and mysql), no such error is found.