If i download installation files on this network, when i try to install software i get:

Installer integrity check has failed. Common causes include
incomplete download and damaged media. Contact the
installer's author to obtain a new copy.

More information at:
http://nsis.sf.net/NSIS_Error

I can download the files on my home network, and i am using the same machine.

Also alot of flash, windows updates and bbc iplayer doesnt work.

Could blocked faults be at fault? I have found the ports for bbc,

If so does anyone know the ports that NSIS uses?