When the following message in the output of the Mageno Resolution.
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.
SOLUTION : delete the following file from your /magento/ installation
If you look on the ftp solution to the Magento root folder is a file named maintenance.flag.
Deleting this guy is normally connected.
In my case I woke later that during installation error template once told me this happens .. ^^