Some of our older remote sites are connected via ATM. Two or three T1s come into an Cisco 8510, and from there a 155mbps OC3 connection over fiber to a 3640 router. Lately, I've been noticing that pretty much every one of them is showing what I think is a rather high receive error count on the 3640 end of the OC3 connection, and it all seems to be CRC errors. Not much of any errors are showing up on the 8510 end of the OC3 connection. For example, one site yesterday late afternoon showed 63, 763 receive errors for the day. Several others were in the 20Ks. I'm not really certain what the cause might be, or where to start. Can anyone help?