error connection with spanninjg tree

Hello ,

we have recently configure Vlan for all swichs and  Spanning tree  is running , suddenly we obtaine the error message like :

Jul 20 08:17:23 vox-switch20-1 TRAPMGR[trapTask]: traputil.c(721) 6158738 %% Gi1/0/3 is transitioned from the Forwarding state to the Blocking state in instance 0
>Jul 20 08:17:23 vox-switch20-1 TRAPMGR[trapTask]: traputil.c(721) 6158739 %% Gi1/0/3 is transitioned from the Learning state to the Forwarding state in instance 0

The Gi1/0/3 interface is only interface connected with own router .

Thanks for advices .

Best regards