The ambush feat Gloom Strike (Drow of the Underdark 54) has as its benefit
Your sneak attack creates an aura of magical darkness that impedes your target’s vision for 3 rounds. The target takes a −4 penalty on Spot checks and treats all other creatures as having concealment. Neither darkvision nor low-light vision pierces this effect, though the ability to see through magical darkness does. Any spell with the light descriptor suppresses the effect.
Is the concealment generated by the feat Gloom Strike sufficient for a creature to use the Hide skill to hide from that affected foe? If so, after hiding can the hidden creature deal sneak attack damage to the affected foe?