I had a project initially created in XCode 3 and used it successfully in XCode 4 Developer Preview version.
After upgrading to XCode 4 release, any time I try to run the project on the device, I get a "Argument Invalid" dialog. Except it doesn't tell me what argument.
How does one figure out what is wrong and why I can't run the app on my device any more?
Base SDK is set to 4.3 Deployment target set to: iOS 4.2
Ok, I have just managed to sort this out as I was having the same issue. This may not help you, but for me it was because I had a symlink inside a folder included in the project. I've removed this, and now it all works fine. Interestingly it works fine on the simulator in this case.
I've filed a bug with Apple on the issue (#9168893).
Just clean your producto
Menu>Product>Clean (Shift+Cmd+K)
I got the following message argument is invalid in response to some kind of USB weirdness. Sometimes it goes away if I unplug and replug the device, but what turns out to fix it more reliably is to start up iTunes. Usually, when I do this, the problematic device doesn't appear in the DEVICES list at first, but does after a few seconds, and once it does, the device and Xcode get along fine.
