Delete local data won't delete your saves. Even if it did, and if you're worried about it, go grab the saves and back them up. They're in "C:\Users\YourName\Documents\my games\Terraria" in Win7.

But they won't be deleted, steam doesn't delete saves, or at least it never has any time I ever reinstalled a game, which is quite a few times.

So, my suggestion: delete local content, reinstall. I bet it will solve your problem.

 

okay i did that, deleted local content and reinstalled. Same issue. Press play, my profile icon goes green like im ingame, then turns blue a few seconds later.

http://www.youtube.com/watch?v=6O5QY6TXqj0&feature=youtu.be

 

Your games are saved inside "My Documents" folder. Search there, backup, redownload the game.

 

Hm, I checked the steam forums. Is this your thread or somebody elses?

http://forums.steampowered.com/forums/showthread.php?t=2971524

If it isn't yours, might be worth checking the .NET framework and re-installing it. Something might have corrupted or gone wrong with your current install of it.

 

Terreraria's detection of .NET (4) and XNA isn't the best, from what I saw when I was active on their support forums, you may just need to uninstall those both and then let Steam automatically install them for you after a reboot (and attempted launch).

 

I'd uninstall all of those.