JOEL - One prophecy that might satisfy your question is found in Judges 13:5, where it is recounted that an angel promised Samson's mother that Samson would "begin to deliver Israel out of the hand of the Philistines." However, because of Samson's failure to live according to his Nazirite calling, this prophecy was never fulfiled. Samson consorted with prostitutes, married a Philistine, ate unclean food, drank wine, and allowed his hair to be cut. Therefore, it could be said that the angel's prophecy was nullified because of Samson's unrighteousness behavior.

I can give you another example, where a prophesy was not fulfilled because a people became righteous. The one about Jonah, who was told by God to prophecy to the people of Ninevah that they would be destroyed in 40 days (Jonah 3:4). God changed things, however, when the people repented and He chose to spare them - much to the chagrin of that imperfect (yet still divinely called) prophet, Jonah. So this prophecy was not fulfilled because of the righteousness of the people.

God told Moses that He would rescue His people from the Egyptians and lead them to a land flowing with milk and honey. But the fulfilment of this prophecy was postponed, because of their lack of faith and unrighteous behavior and it took more than forty years for them to get there.

These examples display the conditional nature that can be attached to many of the prophecies of God. In many cases human actions and choices can alter, postpone, or prevent the fulfillment of prophecy(See Jer. 26:12-13, 17-19).

Through prophecy God could say that a people will live and fluorish, but if they comit iniquity they have no promise:
"When I shall say to the righteous, that he shall surely live; if he trust to his own righteousness, and commit iniquity, all his righteousnesses shall not be remembered; but for his iniquity that he hath committed, he shall die for it." (Ezekiel 33:13, See also Jer 18:8, 10).