3.12NA destroyed my IPv6 capability.
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I use a 6-in-4 tunnel (from SiXXS), and the 3.12 firmware seemed buggy regarding the saving the DNS servers for the tunnel. I could not get it to save the automatic DNS setting, instead I had to enter something manually. And the tunnel did not work even after that...
The firmware also caused random intermittent (DNS?) failures when surfing normal IPv4 internet web sites.
Reverting back to 3.11 removed both problems.