Hello.
I never had this problem until nearly 2 days ago. As soon as I attempt to connect to a server, it tells me that "connection to the server was lost" in the middle of the download of the resources, sometimes at the start. Sometimes I get to login to the server (after several attempts), but I would always get disconnected after a (short) while. I can assure you that this is not due to my Internet. Although something tells me it's related to the recent update to 1.5.6.
I hope to hear from you soon, and thanks in advance.
Kind regards.
Edit: The disconnection message comes under "Error [CD16]", figured it would help.