If you encounter a problem with Anki, please try the following steps in order:
1. Restart Anki
Please close Anki, then start it again.
If you are unable to close Anki because of an error message, you can either terminate Anki using your task manager, or restart your computer. Anki saves periodically, so you should not lose more than a few minutes of work in most circumstances.
If the problem does not occur again, you can skip the following steps.
2. Check add-ons
Please close Anki, then start it again while holding down the shift key. If the problem goes away, that indicates an add-on is causing the problem. Remove any add-ons you don't need, and disable half of the others. If the problem continues, try the other half. Repeat the process until you've figured out which add-on is causing the problem. Then please report the issue to the add-on author, using the Copy Debug Info button, and pasting that into the report.
3. Check your Anki version
You can find the version you're using in the Help>About or Anki>About menu. If the version you're using is not the latest version published on https://apps.ankiweb.net, please close Anki, install the latest version, and then start Anki again to see if the problem has gone away.
If you're using Linux, please make sure you can reproduce the error using the packaged version on the Anki website, as distros often distribute broken versions.
4. Check your database
After restarting Anki, please try the Tools>Check Database menu item to make sure your collection doesn't have any problems.
5. Restart your computer
Sometimes restarting your computer may help.
6. Change the Video Driver
Crashes and display issues can be caused by the video driver. Changing to a different video driver in the preferences screen or via the gldriver file may help. Make sure you try all three options.
7. Reset window sizes
Sometimes pressing 'reset window sizes' button in the preferences screen immediately after starting Anki will help.
8. If the problem remains
If you're confirmed you are using the latest Anki version, and are still receiving errors when starting Anki while holding down the shift key, please report the problem, including the next error you receive in your post.