Foxmarks: Error: Foxmarks is busy

From Foxcloud Wiki

You may receive this error if you attempt to synchronize while Foxmarks is still processing a previous (perhaps automatic) synchronization request.

If this message persists for more than a few minutes, it could mean that a previous attempt at synchronization has crashed. Restarting Firefox in this case will probably solve the problem. If you encounter this repeatedly, you may have discovered a bug. Please follow this procedure to let us know about it.