Xcode 4.2 with iOS 5.0 not detecting iPhone iOS 5.1.1

Question

I changed a while ago from Xcode 3 to Xcode 4.2 for Snow Leopard. Everything was fine, I developed apps for iPhone and all was going smoothly until today... I got alert:

The version of iOS on “iPhone Prophone” does not match any of the versions of iOS supported for development with this installation of the iOS SDK. Please restore the device to a version of the OS listed below, or update to the latest version of the iOS SDK; which is available here.

Which is strange, because yesterday I was able with simple "run" test my app aimed for iOS 5.0 (Xcode target 5.0, 4C199) with my iPhone 4S, which has iOS 5.1.1 (9B206) for quite some time. In Organizer->Devices my iPhone has a yellow dot suggesting that something is wrong. I don't think I did something unexpected, just came, turned mac on and fired up Xcode... any solution?

I've read that, but as I said - I was using new Xcode for few weeks and suddenly this "non-detection" happened...
I'm stuck, thanks for help.

EDIT:
I found something relevant in this topic on SO, but I'll wait a bit - maybe there is something simpler or more obvious that I missed.

Answer 1

I managed to solve the problem, by:
1) downloading xcode 4.3.1
2) copying from package content SDK & Device Support for iOS 5.1 into Xcode directories
3) run and test on your device

solution found here: iOS 5.1 with Xcode 4.2 and retina in iPad 3