Check the network card you have selected does not have "Large Send Offload" enabled?
1. Click on Start and select run;
2. Write "ncpa.cpl" without "";
3. Once the Network Connections window is opened, right click on your network connection, and choose Properties;
4. Press on "Configure" and navigate to the "Advance" tab, once the network card properties is opened;
5. Disable the option called "IPv4 large send offload";
6. Press OK and exit;
This ensures packets winpcap sends do not look corrupted.
A work around for Large Send Offload enable is in versions > 6.0.0.93.