[SOLVED] Address Book No Longer Syncing with Gmail

For the past few months (as long as I can remember), my address book on my mac has been syncing successfully and regularly with my Gmail contacts. If I add something to gmail, it would change on my mac address book and vice versa.

Then recently it stopped syncing.
Under Preferences I went to Accounts, checked Synchronize with Google, and put in my Google login info. It still didn't sink.

Then I noticed when I quit address book and then restart the application, the checkbox for Sync with Google is no longer checked. (It didn't used to do this.)

Also note that about the same time this issue began, I installed a new wireless router (not Airport). To do this, I ate to disable the firewall temporarily, but I later re-enabled it. I don't think I changed any other settings, nor do I see how this could be relevant...but you never know.

I would also note that Mac Mail is syncing with Gmail fine.

Why does this happen? How can I get it to sync again?

Mac OS X - 10.6.4

Thanks a lot