[Isomorphic]

Sorry, this won't be looked at without a minimal, runnable test case, especially since the other people reporting this seem to have found usage issues in their code (no bug).

[mike_mac]

Ok ... I spotted this on stackoverflow

http://stackoverflow.com/questions/11361550/error-with-adding-removing-smartgwt-treegrid-data-this-data-isgroupedoutput-i

Following the suggestion I updated to the latest build and it works !

So its fixed, even if neither of us new what the problem was exactly :-)