Xbox - Falling through the level & texture trouble

[phex59]

I've got a pretty serious problem with GTA IV that I can't seem to find support for anywhere else, so before I call tech support I thought I'd give this place a go.

 

I bought a second-hand Xbox Core from a reputable games store specifically so I could play GTA IV. The system itself plays other games without any problems, only GTA IV has problems of any kind.

 

There are two major problems, either of which make the game completely unplayable:

 

Textures flicker and disappear constantly when outside (Roman's apartment is fine for some reason). I've heard that there is some texture loss on the Xbox version, but this level makes the game painful to use and makes it impossible to drive effectively.

 

More seriously is the 'touching' problem. I only noticed this one after several (painful) minutes of playing the game as it only happens when Nico is on foot. Every time he bumps into a pedestrian the pedestrian either disappears (which caused me to 'fail' the date with Michelle) or Nico 'falls' through the floor and reappears in the air either directly above where he was standing or over the water about a mile south of the city. Again, this means that the game is impossible to use.

 

Little help here?