Who is your ISP? Comcast's IPv6 implementation works with this version of firmware here.
It's a UK ISP, Plusnet.
Here's my router log (tried it again and it still does not work):
Jan 1 00:00:26 syslog: module nf_conntrack_ipv6 not found in modules.dep
Jan 1 00:00:26 start_nat_rules: apply the nat_rules(/tmp/nat_rules_ppp0_eth0)!
Jan 1 00:00:26 kernel: nf_conntrack_rtsp v0.6.21 loading
Jan 1 00:00:26 kernel: nf_nat_rtsp v0.6.21 loading
Jan 1 00:00:26 rc_service: ip-up 372:notify_rc stop_upnp
Jan 1 00:00:26 miniupnpd[349]: received signal 15, good-bye
Jan 1 00:00:26 rc_service: ip-up 372:notify_rc start_upnp
Jan 1 00:00:26 miniupnpd[432]: HTTP listening on port 34113
Jan 1 00:00:26 miniupnpd[432]: Listening for NAT-PMP traffic on port 5351
Jan 1 00:00:26 rc_service: ip-up 372:notify_rc stop_ntpc
Jan 1 00:00:26 rc_service: ip-up 372:notify_rc start_ntpc
Jan 1 00:00:26 rc_service: waitting "stop_ntpc" via ip-up ...
Jan 1 00:00:27 WAN Connection: WAN was restored.
Jan 1 00:00:35 rc_service: ipv6-up 370:notify_rc start_rdnssd
Jan 1 00:00:35 syslog: module nf_conntrack_ipv6 not found in modules.dep
Jan 1 00:00:35 start_nat_rules: apply the nat_rules(/tmp/nat_rules_ppp0_eth0)!
Jan 28 09:36:02 rc_service: ntp 437:notify_rc restart_upnp
Jan 28 09:36:02 rc_service: ntp 437:notify_rc restart_radvd
Jan 28 09:36:02 rc_service: waitting "restart_upnp" via ntp ...
Jan 28 09:36:02 miniupnpd[432]: received signal 15, good-bye
Jan 28 09:36:02 miniupnpd[473]: HTTP listening on port 44053
Jan 28 09:36:02 miniupnpd[473]: Listening for NAT-PMP traffic on port 5351
Jan 28 09:36:03 rc_service: ntp 437:notify_rc restart_diskmon
Jan 28 09:36:03 rc_service: waitting "restart_radvd" via ntp ...
Jan 28 09:36:03 radvd[475]: no auto-selected prefix on interface br0, disabling advertisements
Jan 28 09:36:04 rdnssd[451]: Get IPv6 address & DNS from DHCPv6
Jan 28 09:36:04 rc_service: rc 483:notify_rc start_dhcp6c
Jan 28 09:36:04 dhcp6c[484]: yyerror0: /etc/dhcp6c.conf 4: syntax error
Jan 28 09:36:04 dhcp6c[484]: yyerror0: /etc/dhcp6c.conf 4: fatal parse failure: exiting (1 errors)
Jan 28 09:36:04 dhcp6c[484]: main: failed to parse configuration file