I think there was a problem with the security certificate. My machine syncronises using NTP every 10 minutes or so and is normally correct to within 500µS. 4 seconds is an aeon in computing, but still shouldn't have caused the error. Do you syncronise using network time? If you're still on a Windows machine there is a (unfortunately graphical) way to set it up, but I've a feeling it only checks at insanely long intervals. Mac & Linux should be able to use NTP (or the jacket chronyd) directly.