hi there:

We are currently investigating this issue but unfortunately we haven’t found a way to reproduce it in a consistent way. iPad 1 is not the problem. If you could please help us with any clues about the workflow you were using to make this happen.
As a side note, the app is not frozen. It just goes into this unresponsive state where some tools partially work (text, transform) but everything else doesn’t.
The workaround for now is to press the home button (to suspend the app), then kill the app from the applications drawer and then restart SketchBook.
Sorry for the inconvenience but feel confident that we are looking into this issue.

Thank you!  Please excuse my tardy reply.  I will watch out for this and also pay closer attention to my workflow if it happens again.  I have always been a fan of Autodesk products.  For about 7 years I used Landdesktop and Civil 3d while I worked for a County Transportation department.  Just loving the art thing now.