Check the tests.log and see what the netstat -s and ethtool ethx has. Also is the 3Ware firmware up to date. Is the iSCSI-R3 version 2.30 and was this upgraded from older version? If it was updated from older version did you delete the Logical Volumes and VG' then recreate (from release notes).

Try to test with different Kernel. Go to Console screen - then Console Tools CTRL.
+ ALT. + T select Boot Options - Select System Architecture - Multi
processor server system (TESTING).