iPhone Could Not Support Development
I just got this error with Xcode 4.0.2 and an iPhone 3G running 4.2.1 (the final 4.x allowed on a 3G). I restarted Xcode and it went through the process of collecting debug information, then gave me a green light. Other answers here say that you may also need to quit iTunes for this to work.
Conclusion: Try restarting Xcode. Quit iTunes first if it was open.
Classic ;-)
- connect the iphone
- Go to Xcode -> Window -> organizer
find your iphone and press "Use for development"
As Jacob said: try adding / removing your device as well
If you still get this error you have an out of date XCode
I had the same problem with IOS 5.0.1 and Xcode 4.2. I restarted Xcode as other suggested. However, I also needed to close iTunes which had started automatically and eject my iPhone from iTunes. Then, restart Xcode and it worked fine.