I started having problems with the PlayStation 3 version of Grand Theft Auto IV this weekend. The game started just fine, the music and art kicked in, and the game would begin to load my save file.
The game would simply hang on the load screen (sometimes with chugging noises coming from the Blu-ray drive). This happened five times in a row before I caught word of a simple fix: unplugging the PS3's internet connection.
(Simply signing out of PSN before playing also works fine.)
And guess what? The fix worked perfectly on the first try. After unplugging my Ethernet port and restarting the PS3, Grand Theft Auto IV started right up with no difficulties. This obviously means that I can't play the game's online mode, but given that the PS3 servers are overwhelmed at the moment, this isn't a real sacrifice.
Given the apparent simplicity of the problem, I'm hoping Rockstar will come up with a quick and dirty patch next week, but we'll have to wait and see. For the moment, disconnecting the PS3's online capabilities seems to work just fine.
Other readers have also suggested disabling your PS3's wallpaper or, in desperate cases, deleting the game's save files and stored game content from your PS3's hard drive. Which obviously means you'll have to re-start your progress with a fresh install.