I've got a question.
 

So, since I don't have the money to buy the game, I decided to rent Assassin's Creed:Brotherhood for my Xbox 360. When I finish the first memory in the second sequence (the one in which you have to defend the hudband) the scene cuts back into the DNA sequence menu, and not to the assassination of Il Carnefice. Can somebody tell me what's wrong with the game?

So youre not able to start the sequence that you are trying for? That correct?
Starting up my game to fully understand the situation.

update: Seems like it show just go straight into it, try replaying the last sequence, or exit to the animus and go back in. Not really sure what else there is to try...

Did you get full synch the first time you completed it? If you didn't and tried again, when you finish it takes you back to the DNA sequence. Just go to the next one and press A.

Yeah I should have mentioned something. I actually did it a second time to get the full synch, but it still doesn't let me do memory 2. It reads ''not enough information to access memory. Search for it in the memory'' or sumthin' like that.
And by doing it again, I meant wasting like 2 hours playing the same mission.

The same thing happened to me the first time I tried to repeat a memory and it took me a while to figure out what to do. I thought what I told you was the solution, but it's so obvious I should have remembered that it wasn't. Try choosing the memory that you just repeated...I know there's some kind of little "duh" trick to it.