ECC = Error Correction Code. This message is just a warning/informational, that SW determined there was an internal single bit error, and then went and correct. This functionality prevents bit errors from being sent, but with a good L2 or data CRC. To detect such errors, high level protocols must get involved, maybe up to application level for recovery. This makes the transmission not very efficent.
These errors are most often caused by small guiches in HW, where aging could be a factor. If these errors continue to occur at an increase rate, then generally a HW RMA replacement is most likely the next step.