I'm using U1 on my phone, currently a Nexus S with Android 4. Everthing worked fine untill I changed my password recently. I can still use U1 on all computers (even without having to type in the new password - ?) but it no longer works on the mobile device.
The error message when I try to log in: "could not check time drift: no peer certificate".
I uninstalled the app, removed the device from the list, reinstalled the app, set the time and date (and timezone) to automatic (as an other thread here adviced) and tried to log on again - the same error remains.