The first step I would probably take is to plug a client into the 2011 and verify if it works from there or not. Are you using CAPSMAN or are the APs provisioned independently?
Every client using the 2011 as a default gateway, fails to establish a secure connection via ssl.
Changing the default gateway to “not the mikrotik”, fixes the problem, but is obviously not a solution, since I want the 2011 to do firewalling, forwarding and so on…
I suspect your problem is not the one you found on Google as that seems to be related to connecting to the Mikrotik itself via SSL and not problems with the Mikrotik forwarding SSL.
Usual problems with SSL is MTU size - can your users access any other SSL enabled sites (MS or eBay for example)?