I have recently bought GTA IV but cannot seem to continue the story. I have done four jobs for Vlad, loads for Roman and a couple with Little Jacob. There are no icons for characters on the map, I have hung out with Roman a few times and also done taxi fares for him until he said there is no more work for me. I have tried restarting the story twice but it didn't work. I looked on the internet and found out that the next thing that happens is killing Vlad but I can't get onto that mission?!