Well I thought I was going crazy.
Today I installed foxmarks on my Windows OS, hours later I tried to install it under linux and it kept failing.
I was really losing my patients. I could not figure out why it wasnt working. I disabled all other plugins, closed all other tabs, everything I could think of.
It shows lots of other people were having the same problem.
The solution is to add
to you /etc/hosts file.
It appears that mozilla are having some issues with either the DNS entry or the servers behind releases.mozilla.org
I just know that this change will cause problems in the future though.