Pc version
Windows 7 and Windows Xp
Fast unlimited Broadband connection

Coop Multiplayer Bugs:

Last level:
Helicopter refused to spawn once.
Eddie player ran back at load point just after secret mission failed and collect the secret object making it now mission succesful and sealing himself indie the room.
Jumping over the cars inside the buildings where the drone is bombing got stuck between car and wall several times.

Level with alley way where car drives down it at you:
The car that come down the initial reation is to shoot it and it blows up blocking off the entire path.
The Inn/Tavern building you do a shooting entry for many times disallowed entry.

Randomly shooting entries:
Somethimes diallows all players to stand beside the doors.
You can't stop standing in front of the door once initiated (in case you forgot something).

At the Bar level where your looking for a particular girl:
Eddies Secret object was inside the pillar making it impossible to do.

All enemies Randomly can do horrible teleporting lag where they can instantly move between behind cover and standing.

When doing Driving missions some cars teleport lag and suddenly you crash head on into a car.

Anytime a mission require you to take down all enimies before it opens the door to get further there have been enemies that just aren't there to be killed therfore never allowing you to get further. Either they fell through the floor or failed to spawn because a mission was restarted.

Some main mission objects can't be done if you restart the chapter you have to exit out of the game and start a new game at that chapter for it to be properly refreshed.

There are not enough join points as having to redo antire chapter just because its multiplayer is frustrating as single player goes from the last checkpoint. Too many game stopping bugs are present to really enjoy a coop playthrough.

Edit: thought of 2 more bugs:

Area where you barricade yourself in a building shooting outside the gang members. One gang membr moved to a place where it was impossible to shoot. He could be heard talking and shooting at the wall of the building.

The area with the burning tanker where you need to move the money bags, the reinforcement cars failed to spawn several times in a row halting game progress.