I have a Windows 7 Ultimate desktop and a MacBook Pro (mid-2010) running OS X Lion (10.7). Firefox Sync works properly on my MacBook Pro, but I have been getting error messages on my Windows 7 Ultimate desktop that say: "Sync encountered an error while syncing: Unknown error. Sync will automatically retry this action." Both computers have the latest version of Firefox installed (5.0.1). I have tried removing the add-on, and deactivating and reactivating the device, all on both machines. All to no avail. The only thing I can think of that I haven't yet tried is to setup a whole new Sync account, but I do not think I should have to go to that extreme. Any help is appreciated.