VM NICs disconnected after failover

Hi,

We've performed a couple of failover tests recently using SRM but noticed that a number of the virtual machines power up but have their network cards disconnected.  This appears to be random, affecting different operating systems and including both e1000 NICs and VMXNet3 NICs.

Does anyone have any ideas as to why this would happen and what we can do to rectify it?

Cheers

Chris