Question about GTA 4?

Okay, so i was playing a little bit earlier and i wanted to do some missions. I successfully did a mission for manny, then i get this text message from some random person and he told me to meet him at some place. So when i went to the place, i saw the arrow, but when i walked into it, nothing happened. It just faded away as i walked into it and reappeared when i stepped back. So i was like whatever, then i went to playboy x's place, and the same thing was happening. And the same thing happened for brucie. Everyone on my contacts list were not picking up. Why does this happen? What does it mean?