The only solution after trying many suggestions was to simply restart the "vz" service (definitely not preferable).
Even doing an ifdown and ifup for venet0 did not help.
ifup venet0
Bringing up interface venet0:
Configuring interface venet0:
net.ipv4.conf.venet0.send_redirects = 0
RTNETLINK answers: Network is down
Some errors from log:
CPT ERR: d2dc60........
service vz start
Starting OpenVZ: failed to load module vzmon [FAILED]
vzmon: Unknown symbol ve_snmp_proc_init
vzmon: Unknown symbol addrconf_sysctl_free
vzmon: Unknown symbol ve_ndisc_init
vzmon: Unknown symbol addrconf_ifdown
vzmon: Unknown symbol ip6_frag_cleanup
vzmon: Unknown symbol fini_ve_route6........
service vz start
Starting OpenVZ: failed to load module vzmon [FAILED]
vzmon: Unknown symbol ve_snmp_proc_init
vzmon: Unknown symbol addrconf_sysctl_free
vzmon: Unknown symbol ve_ndisc_init
vzmon: Unknown symbol addrconf_ifdown
vzmon: Unknown symbol ip6_frag_cleanup
vzmon: Unknown symbol fini_ve_route6
........