Hi all!
I know this topic is quite old, but just to offer some clarification:
Cubase IC Pro does not care if you use WEP, unsecured or WPA, adhoc or wifi access point as long as your network is properly setup. But the choice of encryption might be key to get your network stable. This depends on your network equipment (soft and hardware) and we have no influence on that.
Cubase IC has its own security mechanism to protect your mixer from unsolicited manipulation. This can be set in Cubase > Devices > Device Setup … > Remote Devices > Steinberg Remote SKI
If you type the wrong password, your connection will fail. but this has nothing to do with your network if it is stable.
I hope this information helps some of you out there pinning down where exactly your connection breaks.