Short answer: add 127.0.0.1 to the “Disable Proxy for following hosts/domains” in the network settings on your MAC.
After upgrading to the latest 1password Chrome Plugin, I could not use the plugin anymore.
Trying to unlock, by typing my password resulted in an errormessage “Could not connect to 1PasswordAgent. Click OK to Troubleshoot.”
Problem is that 1Password agent opens a TCP port 6258 bound to the 127.0.0.1 local interface only.
On my mac I’m using a proxy to connect to the internet, there are some entries in the settings to not use the proxy for certain sites, *.local being one of them, BUT the localhost interface was missing (127.0.0.1). After adding this entry, and restarting chrome, the 1password Plugin works again.
Ehhh, as I read just now, this was already covered in a pinned forum entry, bummer. (http://forum.agilebits.com/index.php?/topic/7380-faqs-and-known-issues-with-our-new-browser-extensions/)