As soon as I set him free, he starts to attack us. I can't kill him or talk to him. Help!

(ps3)

You can never trust a dragon that just tried to kill you But in all seriousness I don't really know what to do.

Reload, call/capture the dragon again then make sure all the speech options are taken care of before deciding to release it.

If it still happens then call/capture/talk but before releasing zone out then zone back in and see if that changes anything.

By the way these are only suggestions, not a surefire fix.

If Odahviing is shouted at with the Dragonrend shout he will become hostile.
When you agree to release Odahviing and dont ask the guard to do it, when you activate the pull chain Odaviing will again attack you and the pull chain will be locked , forcing you to load another save file.

- two known bugs from the wiki. looks like you need to reload.

It's okay, I reloaded and its fixed now.