If you are on a home network make sure there are no extra firewalls running. eg when i set up my home network the firewall in the new router didnt let me conect to FL.
@ Slainte: The router is not the problem, I played FL Disco on the same router for 2 years, now I have just changed comps from a XP Comp to a Vista Comp
@ Coin: I installed to my desktop, and I also have it set as ADMIN.