Wooohooo, don't you love changes going forward in the Live version that were never tested and largely unannounced. After a month of it working in the opposite manner, JoV will no longer proc Seal of Vengeance.
From the official patch notes:
Seal of Vengeance and Seal of Corruption: These seals have been redesigned. Only auto-attacks and Shield of the Righteous can place the debuff on the paladin’s current target(s). However, while the seal is active, each melee swing or ability (excluding judgements) that lands on the target will deal a percentage of weapon damage as Holy damage to the target. This damage maxes out at 33% weapon damage with 5 applications of the debuff and scales upward evenly based on how many applications of the debuff are active. This Holy damage deals double-damage critical strikes. In addition, the damage-over-time debuff is now considered a melee attack for the purposes of determining its chance to hit, miss, be dodged or parried.
I've got no confirmation that this has yet made it into the Live build as yet (sorry guys, Europe gets the patch tonight and servers will be up sometime in September) but to be honest it's not an absolutely huge nerf (though I'd hardly call it insignificant). It can really be summed up in one phrase: 'JoV already hits like a truck and we really, really don't want you using it in PvP'.
ADDED: Rasputin on EJ has just confirmed that SoV does not proc from JoV. Goodie.