Do you suspect that the Live CD/DVD Iso file could be corrupt?
I tried adding during the install but it locked up
Leading me to believe that something is up with that ISO/install-
This is obviously a BIG problem with Trinity Desktop not putting their own repos in the distro CD
When I installed Fedora 17 I had to open the terminal and literally tell the terminal about rpm Red Hat Package Manager which is the standard for Fedora. The repo's where automatically in the ISO file and put them in the /etc/yum.repos.d/dir. Do you have that directory?
Having trouble understanding why you used( "apt-get update and it updated") APT on a distro that it's main utility tool is YUM-
I wouldn't use Trinity. So far XFCE has been fine-