Depends what old version you had
The LW site doesn't have old versions for download. Since the update, are you fully connected? Do you see the firewall icon (brick wall)? If you do see it, was it showing with the previous version?

What are your details (forgive the repeat questions!)

OS(Win XP etc)
LW & Java version (help > about LW & you'll see)
Firewall you're using
Modem/router brand & model
ISP
Connection type (DSL etc)
Where you connect from (home, school, student accommodation etc)
Are you sharing a connection with other computers
Is this your first try with LW

How did you have your router set up for the previous version (port forwarding, UPnP enabled or neither)?