I will start by repeating Steinberg's official stance: Cubase iC Pro is not officially supported in Nuendo 5.x, but will be supported starting with v6.
That said, I was feeling particularly destructive today and decided to have a go at it anyway. I am running Windows 7 64 bit with dual installation of Nuendo 5.5.5 64 and32 bit (Because some plug ins don't work in 64. I'm not going to name any names [Dolby Media Meter 2...], so back to the post). Both installations are working perfectly!
Here are my steps:
1. Purchase and install the "Cubase iC Pro" app from the app store on your iPad. While waiting for download and installation, work on step 2 & 3.
2. Download and install Apple Bonjour from this site: http://support.apple.com/kb/DL999
* if you skip step 2, your installation may fail. Sometimes order matters...
3. Follow the installation instructions for Cubase iC Pro to the "t" from this site: http://www.steinberg.net/en/support/content_and_accessories/steinberg_ski_remote.html
4. Ensure your iPad and PC are on the same network, with the same subnet and gateway. Some wireless routers segregate the wireless from the hardwire. Being on separate or segregated networks will prevent you from connecting.
5. Open your freshly installed app on your iPad. You may need to wait for a hot second while it "sniffs" out the broadcast from Bonjour. Once the system is identified, connect! You will be prompted to enter a password if you locked Nuendo in the "Device Setup -> Steinberg SKI Remote" menu during step 3. Once connected you will also notice the connection is established and verified as a listing in the "Steinberg SKI Remote -> Devices" window.
It would appear you may have multiple connections, but I only had one iPad to work with while setting this up. I will follow up in a couple days once my copy of Nuendo 6 arrives with a report in a fresh thread entitled Nuendo 6... Good luck to anyone else out there who wants a nice mobile studio solution.
Please vote if you are successful or not! I would love to see how many people are successful.
Last item of business: Steinberg, please poke Yamaha in the eye and tell them to hurry up with Nuage already. I'm way over my DM2000.