I am having a similar problem.
I have a high end gaming computer that ran 4 at maximum graphics without lag.
When I first installed GTA 4, a small console popped up when I opened 4. And then it would open.
Then I got EFLC, and when I opened 4, it would open 4, no console, and have the option to play 4 or EFLC.
After a while, I did some car modding, and then the game glitched or something and nothing would render.
So I had to re-install GTA 4, and I'm back with the console which now opens social club so I can launch the game, and EFLC is separate from 4.
However, when I open 4, sometimes the console just stays, and nothing happens. When I do get through to the game, it takes a much much longer time to get into game-play, and that now has a lag spike every 30 seconds to 1 minute. Then, after maybe 5-10 minutes the game freezes, and a window pops up saying that GTA 4 has stopped working. No error message pops up with a code like some other people get. I am still running the game at max graphics.
I would really appreciate any help.
Processor: Intel i5 quadcore
64-bit operating system
Windows 7 ultimate
The Graphics card is a Nvidia.
I have 2 fans,
A Corsair Vengeance headset,
A Roccat Kone pure mouse,
And A Razor keyboard.
The computer was custom built, ordering parts from PC case gear.