ICX7450 switch STP Loop

We have ICX 7450 switch as distribution switch and below that we have 5 nos HP 5120 as access switches  in a Ring Topology. We have connected one port of 7450 to HP Access switch one and another is connected to access switch 5. If i connect both the link i found STP loop and if i disconnected one of the link, the network found stable. Earlier it was Cisco switch and now we are replacing the same with Brocade.Please suggest.