wireless networking - Can't get an IPV6 ip address with any 802.11g adaptor

I've recently been going dual stack with IPV4 and IPV6 where possible since my isp supports ipv6rd, as does my router - an Asus RT-N56U on firmware 3.0.0.4.374_979 (which is the latest at the time I asked this question). Some of my systems arn't picking up an ipv6 address, and the only common thread I can find is they're all using 802.11g to connect. So far, I've tested a Thinkpad R60 on xubuntu 13.04 and lubuntu 13.04 and 13.10 with intel 3945 abg and and a Thinkpad R61 on windows 7 with an intel 3495 abg and a WUSB54G v4. I believe there's a second R61 that dosen't have an ipv6 address either running XP, but I haven't checked closely to see if its enabled. The R60 connects to ipv6 fine on a wired connection. IPV4 works fine in all cases.

On the other hand, all my other systems that are connected over 802.11n, using ralink, intel or broadcom nics work fine with ipv6, getting a proper ipv6 address automatically with no additional setup. I believe I'm using ipv6 router advertisement (or whatever the default automagical ipv6 setup method is)

As such I've ruled out being the OS (I've tried two different ones, and ipv6 works on a wired connection) drivers or network stacks (since the OSes would use fundamentally different drivers) as well as hardware (tested two different laptops with two different network cards). I'm stumped.

Is there some fundamental incompatibility with ipv6 and 802.11g hardware? How would I troubleshoot this?

For completeness' sake, these are the router side ipv6 settings

EDIT As advised by the comments, I tried setting the router to legacy mode - my 802.11 n gear is still in ipv6, and the windows 7/R60 system is not. This is rather curious, and rules out the protocol alone.

Update 2: Tested pinging 224.0.0.1 on 3 systems and 4 NICs

+--------------------+----------------+----------------------+--------------+---------------------------------------------------+--+
|       System       |      NIC       |         OS           | IPV6 Working |                  Ping 224.0.0.1                   |  |
+--------------------+----------------+----------------------+--------------+---------------------------------------------------+--+
| X220               | Intel N1000    | Windows 7 64 bit     | Yes          | 100% loss "PING: transmit failed.General failure" |  |
| R61                | Intel 3945 abg | Windows 7 32 bit     | No           | 100% loss "Request timed out"                     |  |
| R61                | Intel WUSB54G  | Windows 7 32 bit     | No           | 100% loss "Request timed out"                     |  |
| Asus P8z77 Desktop | Ralink AR9845  | Windows 8.1 64 bit   | Yes          | 100% loss "Request timed out"                     |  |
| Asus P8z77 Desktop | Ralink AR9845  | Kubuntu 13.04 64 bit | Yes          | 100% loss - no error message until ctrl-c         |  |
| Router             | -              | -                    | -            | 100% packet loss no error message                 |  |
+--------------------+----------------+----------------------+--------------+---------------------------------------------------+--+

Update 3: I did a minor change to my network, and added a second router to my network , my trusty old DDWRT, set up as a pure access point, and set as a DHCP forwarder. IPV6 works perfectly there. While this dosen't fix my initial issue, I ought to be able to get data off the same system on a lan where it dosen't work.

I do believe we can rule out the protocol - might be a router issue instead.

Answer

Apparently that version of the firmware was at fault. 3.0.0.4.374_2239 came out today, and flashing to it solved the issue. I'm getting IPv6 on my 802.11g adaptors with no problems whatsoever.

Interestingly, this isn't mentioned in the list of issues that were fixed.