New Gigabit network adapters have a feature called TCP/UDP/IP "checksum offload", which allows the network adapter to calculate packet checksums, thus increasing the system performance and decreasing CPU utilization. Since CommView intercepts packets before they reach the network adapter, the checksum appears to be incorrect. This is normal and the only thing that it might affect is the reconstruction of TCP sessions and only if you changed the default "Ignore incorrect checksums" option (see
Setting Options for more information).