The error message is an informational message saying that the switch received a packet with an invalid
checksum value and dropped it.
Unfortunately its very difficult to know where this is coming as the hw asic does not have the ability to track the source packet since its dropped in hw. The only way to determine this would be to run a sniffer and try to capture the traffic. One thing you can do if you have other cat6k switches is check those and see if you see the error, if not, then it might be something directly attached to this switch.
