Hi Thomas,
I'm using ESXi 5.1.0, 799733. VDDK 5.1.1. Seems to be all up-to-date version.
Further I've noticed is that when I using multi-threads to VixDiskLib_Read(), there is a higher chance to get the VIX_E_HOST_NETWORK_CONN_REFUSED error, although I'm following the Multithreading Considerations.
I'll try to go through some logs and share more info if I got something interesting.