Things to check/try

1. Check release notes 5.x, 4.x, 3.x
2. Check the reported bugs
3. Running latest stable version? tiki-admin.php?page=general
4. Is database up to date? A note will appear on tiki-admin.php if DB structure is out of sync with Tiki version (3.0 and up)
5. Is your database corrupt? -> Repair database
6. Clear all Tiki caches tiki-admin_system.php?do=all
7. Clear your browser cache with Ctrl-F5 (i.e. hold down the Control key and then press F5)
8. Clear your browser cookies (search the web for docs about your specific browser)
9. Try another browser
10. Check your error log (File/folder permission problems will be typically logged here)
11. Are your file and folder perms ok? Run sh setup.sh if you have shell access. When you update your files, via SVN or otherwise, the file permissions may no longer be OK. -> File and Folder permissions
12. Logout & log back in
13. Check integrity of your files
14. If you changed a server setting, did you restart Apache?
15. Change the theme (especially if you are using custom theme)
16. Try to reproduce the problem on a Tiki demo site. If you can reproduce, then, please report a bug
17. Try http://profiles.tikiwiki.org/Debug_Mode_Enabled

Locked out of Tiki

and I can't go to profiles to enable Debug Mode

1. Go to phpMyAdmin (or the equivalent)
2. Find the table tiki_preferences
3. Edit the values from above.
   • Example: error_reporting_level -> 2047

You should also empty all *.tpl.php files in templates_c/

Blank pages

The most common cause of a white screen (no error message, but no content displays) is insufficient PHP script execution memory. A minimum of 16MB is required. Check your phpinfo page or contact your server admin to make sure your site meets this requirement.

Forgotten admin password

Lost admin password

Broken theme

http://themes.tikiwiki.org/Template+Tricks#I_broke_my_theme

Module breaks site

If you add bad content to a module, it could break your site. If this happens, stop using that module (via phpmyadmin)