I must admit I struggled over this passage I came upon the other day:
"... I tell you the truth, you will not finish going through the cities of Israel before the Son of Man comes."
I did some research and found a good article explaining this passage in context. The author debunks the first few theories before explaining that "the Son of Man['s] [coming]" is actually the destruction of Jerusalem. This is further supported by the urgency with which Christ makes this statement as well as the beginning of the chapter, which is about Christ's instructions to the twelve disciples to go and preach in Israel. This is important because Jesus knew that the disciples didn't have much time to preach, because the Romans destroyed the city of Jerusalem in 70 A.D (http://en.wikipedia.org/wiki/Siege_of_Jerusalem_(70)) Further evidence that Christ is not, in fact, referring to His second coming lies in the context of verses 5 and 6 "Do not go among the Gentiles or enter any town of the Samaritans. Go rather to the lost sheep of Israel." Jesus had instructed the twelve disciples to preach the news first to the Jews and then to the Gentiles. If Christ had not even told them to preach to the Gentiles yet, why would He have returned back to Earth before the disciples could finish preaching in Israel? Remember, Christ said that the Gospel must be preached to every nation, to Jew and Gentile alike. This makes it clear that Christ was not talking about His Second Coming, but His coming at Jerusalem to carry out the punishment for Israel's crucifixtion of God's own Son.
Whew :) These were some complicated times and are some complicated Scriptures. Now I see why you can spend your whole life studying the Bible and always learn something new.