Need help with ASYNC_NETWORK_IO
Reboot the offending client. Simple.

ASYNC_NETWORK_IO causes the server to slow down because the client can't consume data quick enough: the network buffers fill up.

FYI: CXPACKET is expected with parallelism. Not sure of current state but IIRC excess of there can be caused by hyperthreading.

Have you rebooted the client yet...? :-)