Yep, it's happening again today - interesting that the connection problems today happened at the same time yesterday.
Anyway, here was the reply from MC from my complaint yesterday:
Dear CM5280,
Thank you for your interest in Cities XL.
This is due to a temporary server slowdown.
Quit the game and connect again in a few minutes.
We apologize for the inconvenience.
Best regards,
The Cities XL Support Team