Cannot Connect

I am reasonably certain that this is not an issue with my computer. However:

Today, I was attempting to connect to a server and received a message "Error verifying steam user id ticket"

Things that I tried on my end:
Trying different servers
Restarting steam
Restarting my computer
Following directions on the steam forum for my issue
https://support.steampowered.com/kb_...4100-WEAK-4375

When I tried to play a different game entirely, this problem did not occur. It only happened with FF
I turned off my firewall and tried to reconnect to FF but when I did that, I could not even load the mod. I received the error message "this mod is not available.

I am running windows xp service pack 3
Pentium D 3.2
2gig's of RAM
ATI graphics card

Let me know if you need any other information.... or I just missed something.