The Torah tells is that when stopped at an inn en route back to Mitzrayim with his wife and children, Moshe Rabeinu was attacked by some kind of angel. Tziporah came to the rescue by doing milah on newborn Eliezer.
The Ibn Ezra (4:20) writes that we learn a fundamental idea from this episode: A navi can be wrong! Moshe Rabeinu was the greatest of nevi'im, yet he obviously miscalculated in undertaking this journey with wife and children at that time.
(What exactly Moshe Rabeinu's mistake was is not clear from the text. See Rashi that Moshe should have done the mila on his son before leaving, but Ibn Ezra suggests that the problem was bringing his wife and children along. Their presence gave the impression that the geulah would not be immediate, but would take time to unfold, and Moshe did not want to be separated from his family for such a long period. Moshe had no right to dishearten the people in this way. Meshech Chochma along similar lines suggests that the Moshe brought his family as a way to prove to the people the geulah would happen -- he would not bring his family just to add to the slave population. The very fact that he thought such proof necessary demonstrated Moshe's doubt that the people would as a matter of course believe him, even after being told by G-d that they are ma'aminim. This lack of trust was an error.)
We find a similar idea in Sefer Shmuel (II:7). When David haMelech consulted Noson haNavi about whether to build a Beis haMikdash, Noson told him to go for it. (And let me remind you of the Minchas Chinuch (posted once before) that according to some Rishonim there is a mitzvah to listen to a navi even when he gives advice that was not received b'nevuah.) Yet, that very night Hashem appeared to Noson and told him to go back to David and tell him to stop, as he did not have Hashem's permission to build the Mikdash. Noson made a mistake in his original advice.
I don't think the Ibn Ezra means to throw out the mitzvah of listening to a navi, nor do I think he means to take a position in the Minchas Chinuch's safeik of whether there is a mitzvah to listen to the advice of a navi. What he means is that EVEN THOUGH there is no greater source of insight than a navi, EVEN THOUGH one is commanded to obey the navi, that does not mean that navi is guaranteed to come up with the right answer.
One more EVEN THOUGH, which I think is the more important lesson for us -- The argument that since talmidei chachamim have erred at times in their judgment, therefore QED their judgment is not superior to that of a layperson and can be ignored, does not follow. Just as a navi is the best person to consult on issues that relate to the future of Klal Yisrael, EVEN THOUGH he might err, a gadol b'yisrael is the best person to consult on those same issues EVEN THOUGH he might err as well.
These mistakes -- that of Moshe and that of Nosson -- were no small errors. Moshe Rabeinu's error put the plan of geulas Mitzrayim in jeopardy. Noson's error was with respect to Beis haMikdash, the kodesh kodashim, the central point of avodah. Hashem came to Noson and revealed his error; the geulah from Mitzrayim was directly guided by Hashem's hashgacha and would have worked out somehow anyway -- we don't have that benefit, so how can we trust our leaders? How can we place our faith in their judgment when they have been wrong about issues of great magnitude in the past? I think this question makes a wrong assumption. Just because Hashem is not speaking from burning bushes or coming to people in dreams does not mean he is not working behind the scenes, ironing our whatever errors are made. Jewish history and fate do not hang in the balance of our leaders' decisions alone, whether for good or bad.