This one is a bit odd, and I know there was an issue with the 2014 product that sometimes made SWTOR (Star Wars: The Old Republic) fail to launch.
I didn't have that problem, but as soon as I updated from 2014 to 2015 on my Windows 8.1 machine, SWTOR would not launch.
The launcher.exe program would hang with a half rendered window and no error aside from 'not responding'.
Things I've done so far that have not resolved the issue:
1) Added the path to the game to the exclusions list (which was wiped in the upgrade somehow!).
2) Rebooted (of course)
3) Removed and reinstalled the game entirely.
4) Removed and reinstalled Bitdefender entirely, thinking it may have been an upgrade issue.
5) Run the repair tool for both SWTOR and Bitdefender 2015.
6) Added the full path to the launcher.exe, swtor.exe, and every individual folder in the path to the exclusions list.
7) Added all of the dll files for the game to the exclusions list.
I also found that, if I install Bitdefender 2015 while the game is running, the game continues to run; however, if the game is closed for any reason, it will NOT relaunch. It will simply hang with 'not responding'.
Things I have done that have immediately resolved the issue:
1) Uninstalled Bitdefender 2015.
As soon as Bitdefender 2015 is gone from the system, even without a reboot, SWTOR launches normally, so I don't believe this to be an issue with the game client, but rather with something that Bitdefender 2015 is doing. It also doesn't seem as though Bitdefender 2015 is deleting files, as was the issue with older versions, as after removing Bitdefender 2015 the game functions normally.
My second computer is still running Bitdefender 2014 and does not have this issue and SWTOR launches normally.
If I put Bitdefender 2014 on this computer, it does not have the issue and SWTOR launches normally.
If there isn't a fix coming for this or a fix in place that I just haven't found, I'd like to request a refund as I only just purchased the upgrade/renewal a couple of days ago and I'm not willing to not be able to play the game.