Ok... I know about the difference between the base/active SDKs and the deployment target. I have my base SDK set at 4.0 and the deployment target set at 2.0. I am not using any APIs post 2.x, conditional or otherwise. Since I can't debug on a 2.x device, after building it, I use the iPhone Configuration Utility to install the app on the device, which it does just fine. Problem is, it doesn't run! I just get a blank screen. The main window never comes up!

Now before you ask...

1. I had this same problem with the iPhone SDK 3.x. I upgraded to the 4.x hoping it would be solved. It wasn't.

2. Yes the provisioning profile is installed. (Couldn't install the app if it wasn't.)

3. This same compiled app works fine on 3.x devices. Same with 4.x devices. Just not 2.x devices.

4. Again, no I am not using any post-2.x SDKs. To prove this I created a brand-new, window-based app from the 'New Project' dialog and the only changes I made was the background color of the window (to prove the XIB loaded) and I set the deployment target to 2.0 (It's still compiled against the 4.x SDK though.) Again, it runs fine on 3.x or 4.x devices, but just a black, blank screen on 2.x devices.

I've tried this on three separate 2.x devices included one freshly restored. I've used three separate dev machines (MacBook Pro with the 3.x SDK, MacBook Pro with the 4.x SDK and a Mac Pro with the 3.x SDK.) Same result every time.

I am stumped.

The fact that even an unmodified project doesn't run really has me confused. Could it be the XIB file? Did they change the format from 2.x to something newer in the 3.x SDK? If so, how do I set it back to 2.x. (Again, this is just a complete guess.) But I'm really stumped!

Mark