I posted that issue on the French forum, but could not really fix it. The remote agendas (Google and Yahoo) time to time stop to be connected with Evolution on my OpenSUSE 13.1 Gnome OS 64bit. I get the following message from Evolution:

Error loading calendar
The calendar is not marked for offline usage.

I managed twice to make them work again by resetting wifi, router, network, etc. But I didn't really know what I was doing. Now the agendas are down again, but I can't figure out how to turn them on.

Any idea?