Thanks for your response Ben.
I called Mr Larue from NI France (ref 300258) but he couldn't help me
because my dll perform TCP/IP exchange with a special device.
I solved the problem by suppressing step by step the clusters, tables and others vi's call.
I use tables to print my device informations (soft version, serial number...).
It seems to be the problem for me: dll call with "ElementName" (write mode) from "PropertiesNode" of my tables.
I hope this can be helpful for other people, it works for me.
I don't know if it is a known problem and if in future version the bug is suppress.
I actually work with version 7.1 and soon (I hope) with version 8.0.
I join a picture of my VI, I can't attach the project for confidentiality reasons.
Happy Halloween,
JethroTulls.