Xcode : failed to get the task for process

This is for an existing app that compiled and distributed multiple times. Since updating to Xcode 5 I have this error popping.

1. I have my developers profile selected in the Code Signing for debug.
2. Deleted the Derived Data a few times.
3. Quit a few times
4. Downloaded and tried to re-add my Developers certificates.
5. Reset my computer! And checked updates
6. Tried using black magic!
7. The Scheme > Build Configuration is set to Debug

The odd circumstances I am compiling to compile to iOS 6.1 so I can run on my iPhone 3GS - the base is SDK iOS 7? Could this be an issue? I just need to test it before finding a newer phone to before change it to iOS 7.

I have not accepted the answers above as there was a chain of issues that I needed to resolve:

1. Third party SDK not set as a distribution.
2. Third party SDK not set to arm64, which I think I caused as I in vain to fix the issue compiled to arm64.
3. Needed to complete clear out any old certificates and add new ones from Apple. Good thing to do.
4. Xcode 5 hides the certs and profiles in preferences now I think, which added frustrations.
5. Then making sure the correct provision profiles are selected across the debug and release settings in your Build settings.

As always thanks for peoples help.