Hi mate,
One initial thing to check is DNS - make sure all hosts in the HA cluster are resolvable from all other hosts (and vc) - use only lowercase for the hostname entries i:
/etc/vmware/esx.conf, /etc/hosts, /etc/sysconfig/network and /proc/sys/kernel/hostname
Also check hostnames are lowercase through VI (configuration tab | DNS and routing)
Hope this helps.
Dan