I have a WS-C4510R running 12.2(20)EWA1 with dual SUPs V.
There are also 10/100 48-port network modules and two 10/100/1000 ports with fiber uplinks to the MDF.
Every now and then, this switch will stop forwarding packets. Hosts on the same VLAN and connected to the same NM cannot talk either. If I reboot the switch, then all connectivity is restored. Sometimes, I can wait about 15 mins and the switch will resume operations. No syslogs are logged to indicate any event.