It was because I was in instruction-wise operation mode. Unchecking Debug → Operate By Instruction solved my problem.

Hi Rondog, I'm sorry to reply later...

I resolved the problem already.

It's about implementation of the PROPTree...

The function of the PROPTree what create and return the elements of the tree must return the last index of the tree, and I return a m_Symbol.size() in the PROPTree::atom(), so that was the error.

I'm very grateful about your help.

Thank You.