- Run the updater
- Update your graphics card's drivers
- Try switching to windowed/fullscreen mode
- Turn on/off the vertex buffer
- Disable/enable sound
- Try changing GUI skins
- If all else fails, try reinstalling the game
(4-7 are done via the setup program)
To update your drivers, goto your graphics card company's website and download them from there.
Do not use the drivers that came with Windows. They're garbage.
If you do resort to reinstalling, first uninstall the old one remembering to back up any logs, screenshots, quest notes in the data folder, and options in data/options you may want.
We have made Troubleshooting guides for all OSes:
Troubleshooting_guide_for_WindowsTroubleshooting_guide_for_MacOSXTroubleshooting_guide_for_LinuxSo, you got an "access violation" at some big number, good for you. Collect them all and maybe you'll win a prize.

Search the forum for that number, and see if you can find something. However, more often than not, the number is useless. Ask us for help, and we'll try to find out what's doing it.