After a while, client no allow to read mail

I am using my notes client to read the mail. After a while, I can NOT open the mail, and it displays an laert box: “You are not allow to do this operation” or something like that (it is the spanish version).

I do not have a clue about what is wrong.

The only point is that the log.nsf on local show the execution of the Dynamic Client Configuracion

Thanks

Dominique