Hi Sergey,

>>It would help if you post code that reproduces this problem.

Essentially:

oParentNode = Tree.Nodes.Add(,,"A","Parent")  && Add Top Level Node
oChildNode = Tree.Nodes.Add("A",4,"B","Child") && Add a child to it
oParentNode.Parent = oChildNode  && Error 

The OLE error in VFP6 is 1429 'This would introduce a cycle'
In VFP8 it's 1426 'Member not found'

The above is a simplistic example which could easily be trapped but the VFP6 error provided an easy way of detecting the same situation when the node being assigned as the parent node was a much more deeply nested descendant.

Regards,
Viv