Xcode: failed to get the task for process

I've run in release mode my app on a iPhone with Xcode 4.

Everything worked great until when I switch to the simulator and I switched back to the iPhone. After switching back, the app is launched on the iPhone, but the home screen is displayed immediately after and in Xcode I get:

failed to get the task for process 

I've tried to remove/add Entitlements file, delete app and restart Xcode but nothing to do.

I am betting that your release mode includes compiling with your distribution certificate, which disallows this behavior (you wouldn't want some random fool hooking into your app after downloading it from the app store). Compile with the development certificate instead. You can change this in the building settings under code signing.

Change the profile for code signing. Select your project, go to Build Settings > Code Signing Identity. Switch to other developer profile.

If anyone is having this issue but is sure they have their certificates and code signing correctly set up, check the capabilities tab when you click on the project (i.e. next to build settings tab, build phases tab, etc).

In my case there were broken links for Game Center and In-App Purchases that needed fixing (by clicking the "fix me" buttons) to solve this issue.

I had a the same issue and after reading the above answers all I had to do was go to Build Settings > Code Signing > Provisioning Profile > None and was able to ran the app on my devices again. Hope this helps someone else out

To anyone who comes across this: After reading this, I attempted to solve the problem by setting the Debug signing to my Development certificate only to find that deployment was still failing.

Turns out my target was Release and therefore still signing with the distribution certificate - either go back to Debug target or change the release signing to Development temporarily.