> What is the cause? I use version 1.3.2 since months on Ubuntu 12.04.

So 1.3.2 was working fine for a while and then later the problem started to
occur? That would point towards a change on the server.

Either way, without further information about where the 404 error occurs it's
not possible to root cause the issue. It's not a known problem.

Can you perhaps attach a syncevolution-log.html file that contains the problem?

If it contains private information, then you can send it to me ("patrick.ohly
at gmx.de") directly and I'll treat it confidentially.