"Error building Admin Menu" problem is related to Joomla 2.5 / 1.7 / 1.6, this is a Joomla core issue and affects different extensions during installation.
This can also happen if you have tried to install DJ-Catalog2 for Joomla 1.5 on Joomla 2.5 by error, and then installing the correct version for Joomla 2.5.
If this happened to you while installing DJ-Catalog2 extension follow this steps to fix it:
If this is a production site do the backup first. Use for example great Akeeba Backup extension.