thanks a lot for your help, but there is not an STP issue or a loop.
before I have reported the issue I made many test in order to be sure that there is not a configuration problem,
let´s suppose that there is a loop, so way the conections to the routers don not turn on?, becouse the cpu utilization is to hight? well its possible but there is nor the roort couse.
I belive that is a bug in the simulation´s software, however only to show you that the problems does not the STP or a loop problem I created a new topology with single interconection between switches, were I disabled the STP, and I have got the same issue.
in the attached you can see the results.
best regards.
Ricardo Sanchez.