Pretty much stated above. When applying the filter
Sounds like checksum offloading.
In a nutshell: the NIC card does the checksum calculation just before sending the packet on the wire.
There's no actual problem. See the referenced links for how to disable the verification of the checksum in Wireshark.
(Ps: Please use "comment" rather than "answer": See the FAQ as to how ask.wireshark works)
For right now, I'd disable checksum verification in Wireshark if the false alarms bother you.
One point of interest...if the machine in question is running Windows Server 2003 SP2 or Windows Small Business Server, there are specific client/server performance issues related to those features. See http://support.microsoft.com/kb/948496 if you are running either of those operating systems.
answered 26 Oct '10, 10:46