QuoteIPV6 aren't supported in 2.0.x and won't be. This is an error fixed for 2.1, but it won't be fixed for 2.0.x.http://www.simplemachines.org/community/index.php?topic=543919.msg3862603#msg3862603
http://www.simplemachines.org/community/index.php?topic=548191.msg3888245#msg3888245
if it is so and ipv6 is not supported by forum, you should disable ipv6 on server and/or remove aaaa from dns.