If your using the new crimson driver however still that is what is causing the problem. If you lower your AA settings to medium or lower it will work around the issue.
This is an issue specifically with the Crimson driver version 15.11. These are the only options.
1. Lower AA settings to medium or lower
2. Uninstall the Crimson driver and go back to the previous driver which you can get from the AMD website.
3. Install the Crimson driver beta 15.11.1 which resolves the issue altogether, however since the driver is beta install at your own risk and may have to uninstall the other drivers first.
4. Wait till 15.11.1 officially released and upgrade.
This is a specific issue with the driver which AMD probably figured out and resolve in the next version.
Here is the thread that talks about using the beta version that fixes it:
http://www.swtor.com/community/showthread.php?t=856556
