apt-get won't update...

[Dylan]

I am sure this has been covered before, but I am having difficulty 
sorting this one.  I was updating a few packages when an error was 
raised with apt-get.  It suggested that i run the command:

apt-get -f install

Sure enough, it seemed like it corrected the issue, but since then I 
cannot update or install using apt-get.  Can anybody help me with this.

Thanks,

Dylan