PP8600 fiber ports failing

rc2k8x1000BaseC 8 port fiber blade running software p80a3710.img. We have a few times now seen ports just go out of service. Nothing indicating that the port is dead other then no activity to far end. Swapping GBIC's sometimes works, swapping ports always seems to work. I have tried disabling and enabling the ports but I usually have to insert into a vacant slot before I can get the communications active again. I am wondering if anyone else has seen this sort of issue?

Thanks again,

John Mitchell