Addon Installation works flawlessly. When trying to set up, the general username and password are accepted and the addon asks for the sync key. Entering the sync key returns an unknown error and the addons returns me to the general username/password dialog. Here, confirming the already entered data returns an unknown error as well and no more confirmation is possible except exiting the application. Tested version is Firefox Sync 1.7.0 on Iceweasel 3.5.16 (PowerPC architecture).