Are you using FTP (in Global configuration)?
There are some issues with PostgreSQL 8.3 as postgreSQL changed some things. Elxis 2008 has been fixed in order to support postgreSQL 8.3. Prior to 8.3 PostgreSQL databases are supported without problems even by the 2006.x Elxis.Docman is not an genuine Elxis extension. It is a fixed version of the mambo's Docman and might does not support other databases other than MySQL.
Upload component - FailedFile /var/www/elxis/tmpr/install_477d0b4591871/includes_frontend/index.html does not exist!