PS3 DNS Error 80710102 FIX
Occasionally my PS3 refuses to sign in. After trawling through a billion pages I finally found the solution.
Change your DNS servers to 184.108.40.206 or/and 220.127.116.11
All the other settings don’t really make any difference. My router was even set up to put the PS3 in DMZ (Demilitarised Zone) which didn’t help at all. The fault really lies with your ISP, apparently. My original DNS was 18.104.22.168 and 22.214.171.124.
Thanks to amstel78 from the PSN forums.