Thanks for emailing me your log files and your project. The issue you saw was caused by a missing component that is still referenced in other screen files. The immediate fix is to remove the reference to this component. We'll also update WireframeSketcher to handle better this broken references in the future.
Eclipse Kepler may have it's issues, but this was not one of them. If you see other errors or stability problems please let me know and I'll investigate them ASAP.