Solved
Assumption in assembly mode problem !
(sorry for my english 
)
Since i upgraded from creo 2.0 m60 to m130
I realize in assembly mode when i what to add a new part.
I need to click the ok button and re-click on edit definition to have the choice to use the allow assumption checkbox
Looks when you insert the part for the first time it's not allow, just make no sense for me.
Everybody at my office using creo have the same problem.
Thanks
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