Many problems with Star Wars: The Old Republic can be cured by the repair feature, which will automatically check your installation for corrupt files. If your game is not working properly, then repairing is a great place to start troubleshooting.
From the launcher, select the Settings button (shaped like a gear).
A large Repair button will be in the lower left. When you click it, the repair program will inspect all of your game files and redownload any that have become corrupted. This may take some time.