unable to login - connection to login server terminated within a second

Just installed the game on a Win 10 Box, preinstalled with McAfee; Installation worked fine and first Logins, too, but after some hours (and proably ominous updates and installs by the System) I can't no longer log in; after typing the password in the game client, a timeout ist reported after barely a second.
I've already configured exceptions for gameclient and laucher in Windows Firewall as well as in the McAfee NetGuard.
Error log shows:
160127 23:09:15 156 Client[0 [NOENT]]: LoginServer link disconnected (208.95.186.64:7001). Reason: async_bytes_read < 0:read failed:linkQueueRemove(0:No error) (socket error 0: No error)
160127 23:18:03 155 Client[0 [NOENT]]: LoginServer link attempting connect: 208.95.186.96:7001
160127 23:18:04 156 Client[0 [NOENT]]: LoginServer link disconnected (208.95.186.96:7001). Reason: async_bytes_read < 0:read failed:linkQueueRemove(0:No error) (socket error 0: No error)
160127 23:29:15 155 Client[0 [NOENT]]: LoginServer link attempting connect: 208.95.186.96:7001
160127 23:29:15 157 Client[0 [NOENT]]: LoginServer link disconnected (208.95.186.96:7001). Reason: crc != local_crc:read failed:linkQueueRemove(0:No error) (socket error 0: No error)

Has anybody encountered a similar problem?
Has anyone an idea what may be the reason or how to proceed?
Is there a proxy which might be helpful?

(Login from other PC still works, other games - online ones, too - don't seem to have similar problems; Access by WLAN & T-Online VDSL.)