Well, after I’ve checked all the (minor) changes between iOS 5 and iOS6 (on an iPad2) I took the version-jump and made the Update.
And: iC Pro now works correctly - what a surprise! 
However, I just checked the App Store and the App-Details for iC Pro still show iOS 5.0 or later as a requirement! At least for iPad2 version 6 is now confirmed to be required for full iC Pro-functionality.