I have a desktop running Maverick, and a laptop running Lucid. Both are supposed to be linked to my Ubuntu One account.
The desktop syncs fine, but when I started the laptop for the first time in a couple of months, it wouldn't sync any more. The Ubuntu One Preferences window either reports "Synchronisation complete" even though no recent files have been downloaded nor have any test files created in the relevant synced folder been uploaded, or it says "Synchronisation in progress", which does not appear to be happening as it stays like this for ages and the lights on my router suggest no traffic is going through.
Have repeatedly tried disconnecting and reconnecting, and removing the device from the account then reattaching it, all to no avail.