Apparently yesterday's Grand Theft Auto 4 patch unleashed a whole new set of issues on gamers, including a problem with look/spin/stuck keys. Rockstar has taken notice of your complaints and are now offering the following temporary fix (via GTAForums.com):
With the latest Title Update, some users are experiencing a Look/Spin/Stuck Key issue that interferes with user input. The temporary fix, described below, will restore Keyboard/Mouse and XInput (360) controller functionality. Support for DirectInput devices is currently limited. We apologize for the inconvenience and appreciate your patience.
To fix the 220b issue:
A1) Unplug any DirectInput controllers (gamepads, joysticks etc..)
A2) Reboot your computer
A3) Launch GTA IV
If the issue persists, the following instructions are provided as a guide to assist you in deleting the conflicting DirectInput drivers:
B1) Exit game
B2) Go to Start->Control Panel->System->Hardware Tab->Device Manager->Human Interface Devices
B3) Locate drivers for devices
B4) Delete drivers for devices
B5) Launch GTA IV
**Some users are able to reinstall the drivers for their DirectInput devices, with the device attached, and have found that it will work in game. If you do attempt to reinstall your device and the problem resurfaces, please follow steps B1-B5 again.
Hopefully this "fix" works for all of you. If not, I guess we'll have to wait till the next update. :/
