Strange indeed.
Are you on IOS 7 ? Which samplerate and bitrate did you choose.
Even when you set your samplerate to 96kHz and the bitrate to 24bit you should be able to record at least 10 tracks simultaneously → Check this thread Which used iPad to buy for Cubasis? - #6 by Hiltmann - Cubasis - Steinberg Forums
Have you tried restarting the Pad with no other Apps open?
First thing I would suggest is to reinstall Cubasis.
Hope that sorts it out for you.
cheers
Ludwig