Hello people!
Recently I had a similar problem. My FOG solution is:
FOG version 1.2.0 revision 3246
Ubuntu Desktop 13.10 i386
Working with Hosts Management section, creating a host, erasing this host and again creating the host with same MAC I had the trouble that FOG said me that this hostname already exists. In the Host Management section did not appear the host.
The solution is like Tom says. Thank you Tom!!
For me, deleting the registers in fog database with the [I]wrong[/I] host ([I]wrong[/I] means the created, then deleted and then tried to create) in [I]host[/I] and [I]hostMAC[/I] table was the solution.
I searched how to manipulate fog database.
I used phpMyAdmin (searching directly with Ubuntu Software Center).
Then I configure to get access to the fog database (I used blank password in mysql).
Edit /etc/phpmyadmin/config.inc.php
[INDENT=1]Uncomment this line:[/INDENT]
[INDENT=1][COLOR=#3366ff][SIZE=4]$cfg[‘Servers’][$i][‘AllowNoPassword’] = TRUE;[/SIZE][/COLOR][/INDENT]
[INDENT=1]Save file.[/INDENT]
Finally, search the tables [I]host[/I] and [I]hostMAC[/I] and delete the [I]wrong[/I] host registers.
I hope it helps. See you,
T. Capablo.