Now I don't know if anyone else has run up with this but I thought it would be nice to know about it.
This bug happens when two players jump in to the air and GTA 3 starts the cinematic slow-motion, as you all know. The problem is that when the first player's GTA 3 starts the slow-motion the other sees the jumping player in slow-motion but everything else in real-time.
If you have seen the film Scary movie 2 then you should already be comfortable with this time-problem x)
This bug proved to be a very funny one for me and my friend when we had a lan party - I jumped to the air and he drove under me when I was still in the air x)
As for fixing this problem, I suggest getting rid of the slow-motion for it is impossible to use in multiplayer games unless all the other player's games slow down too (which would be quite frustating, imagine a big game where numerous players go jumping, or imagine the "new speed game mode" )