Problems here on Ubuntu/Firefox. No problem with the account set-up. No problem with the Firefox plug-in install.

When I try to add this page, I get the "Adding this page..." but after a few seconds I get another window that has "Zukmo" at the top in large text, but the window is not large enough to contain further text. This latter window disappears after a second or less.

I think the window is asking me to log-in. But I am logged in to Zukmo.

One further thing. Forcing an icon into the status bar without the option to switch it off is a show-stopper for me. It's a decision that doesn't scale. If every plug-in did this, then the status bar would be a mess and its usefulness reduced.