I've installed the latest browser extension w/ Firefox 28.0 on OSX 10.9.2. It installs fine. But, when I click on the key icon in the toolbar, I get a browser window with a dialog box that says "Looking for the 1Password app. The 1Password app must be installed for the extension to work properly." This never terminates. 1Password 3.8.21 is installed and works fine. When I try to update it, that says it is the latest. Do I need to be updating to 1Password 4? I haven't had this long so I'm surprised if I need to buy something new.
I think the problem may have been 1password (the app) opened a dialog box for conflicts that was hidden by another window. It may have been blocking in the browser waiting for this window to close.
Please ensure that you have the version 3 browser extension installed if you are using 1Password 3.
You'll find it for download here:
Please let us know if you have any other questions.