OpenVPN issues on a OpenVZ / Virtuozzo enabled VPS

Error Note: Cannot open TUN/TAP dev /dev/net/tun: Permission denied (errno=13)

Just follow the KB at http://wiki.openvz.org/VPN_via_the_TUN/TAP_device

Error Note: Cannot set tx queue length on tun0: Operation not permitted (errno=1)

As mentioned in the same KB URL, just do the steps below and things should be alright again

vzctl set 101 --devices c:10:200:rw --save
vzctl set 101 --capability net_admin:on --save

Basically the errors are caused by the non-execution of the two commands mentioned above.