This is will be a pretty brief post. I have recently been having trouble with certain websites not fully loading, mainly webpages with dynamic content (eg facebook or twitter) it turns out this was because I was running an older version of JAVA, having now updated to 6.17 it seems to have fixed the problem
SO if you find that certain webpages in firefox will not load or never finish loading try going to
www.java.com and check that you have the latest version installed.
I hope that helps someone