@Manuel I now think that my problem was a network issue. I was on a corporate LAN on 4/2, when I was unable to sync. I've tried today with the same install on a broadband connection and it's worked fine. It looks like it's probably a firewall issue that's not being reported in a meaningful way.
So, to be clear, the client is working fine for me with a broadband connection and local firewall software (McAfee). When I connect using the same laptop via. my corporate LAN, it's unable to sync and the error is "TypeError: <type 'str'> is not JSON serializable".
@Manuel I now think that my problem was a network issue. I was on a corporate LAN on 4/2, when I was unable to sync. I've tried today with the same install on a broadband connection and it's worked fine. It looks like it's probably a firewall issue that's not being reported in a meaningful way.
So, to be clear, the client is working fine for me with a broadband connection and local firewall software (McAfee). When I connect using the same laptop via. my corporate LAN, it's unable to sync and the error is "TypeError: <type 'str'> is not JSON serializable".