We're getting ready to launch some exciting new features and part of that preparation requires that Foxmarks 2 users be running the latest version of the extension (version 2.0.45). This version was released a month ago; the vast majority of users are using it already. It is at least as stable as prior versions, so the upgrade should be painless. Starting later this week users of older versions of Foxmarks will see a pop up message advising them of the need to upgrade.
We recognize that upgrading can be a hassle; we strive to minimize unnecessary updates. Unfortunately, this is one of those cases where we can't continue to support earlier versions of the extension with newer versions of the server. As always, we appreciate your patience and support.
Note that if you're running the beta version of Foxmarks, you won't have to do anything; the beta versions are fine as is.
Also, if you're one of the few users who are still using Foxmarks 1.0.1, a reminder that that system is heading toward retirement.