These are the known list of error messages on a 4006
http://www.cisco.com/warp/public/473/34.shtml#4000_ERRORS
I dont see your type of error messages ...but it clearly indicates that packets were received with an Invalid CRC and dropped and the count is 836679 (which is really high in number)
Are you getting the above syslog message, very often ??
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus