Tor needs your system clock (and your time zone) set to the correct time.
The following firewall software have been known to interfere with Tor and may need to be temporarily disabled:
Webroot SecureAnywhere
Kaspersky Internet Security 2012
Sophos Antivirus for Mac
Microsoft Security Essentials
Videos that require Adobe Flash are unavailable. Flash is disabled for security reasons.
Tor can not use a bridge if a proxy is set.
The Tor Browser package is dated January 1, 2000 00:00:00 UTC. This is to ensure that each software build is exactly reproducible.
To run Tor Browser on Ubuntu, users need to execute a shell script. Open "Files" (Unity's explorer), open Preferences → Behavior Tab → Set "Run executable text files when they are opened" to "Ask every time", then OK. Tor Browser can also be started from the command line by running
./start-tor-browser.desktop
from inside the Tor Browser directory.