Following this thread, and this similar one on GWTW:
http://gwtw-kites.com/forum/topic.asp?TOPIC_ID=12930
I emailed R-Sky expressing my concern that so many (4) Nirvanas seemed to be failing in the same way.
Roger T-G replied to me saying that modern sports kites take a lot of beating and that such failure could be down to wear to the thread from dead launching or tricks like the Comete (??)... He said that for 'safety' (babelfish) they have changed threads now, but that out of all the hundreds of Nirvanas sold worldwide he has not been told of any other failures.