A friend of mine ran into a serious problem where they could no longer progress in the missions of Grand Theft Auto 4. When they went to the yellow way point arrows nothing happened and the mission would not trigger. It seems to happen after “The Puerto Rican Connection” mission when you receive a call from an unknown person. I did a few searches on the web and found several other people having the same problem. Many had to start the game over, but the good news is there is a fix.
In order to trigger the missions again you need to call one of your contacts. It’s probably best to call Roman and book something with him. This should trigger the stories progress. I’ve also read that a manual save can work too, but I know for sure a call too Roman will work. I have not actually experienced the bug myself, but this work for my friend. The bug also seems to effect both PS3 and 360 versions of the game. GTA 4 is still a fantastic game, and hopefully not too many people experience this bug and if they do I hope this helps and hopefully Rockstar will have a fix for it soon.