so i originally set up my development environment, keys, certificates/profiles, etc on my laptop. i then wanted to do some work from my desktop (old dual G4. another post coming, describing how to get XCode to work with the iPhone SDK on a PPC).
anyway, i moved my profiles over to my new machine and added the iPhone as a device i wanted to use with XCode. but when i tried to set the Profile in the Project Settings, no profiles were listed to select from. when i looked in Keychain Manager, i noticed my Certificates were there, but there were no Keys installed. i then realized i didn't closely follow the directions on Apple's iPhoneDev Portal. here's a quote:
Saving your Private Key and Transferring to other Systems
It is critical that you save your private key somewhere safe in the event that you need to develop on multiple computers or decide to reinstall your system OS. Without your private key, you will be unable to sign binaries in Xcode and test your application on any Apple device. When a CSR is generated, the Keychain Access application creates a private key on your login keychain. This private key is tied to your user account and cannot be reproduced if lost due to an OS reinstall. If you plan to do development and testing work on multiple systems, you will need to import your private key onto all of the systems you’ll be doing work on.
simply dragging the certificates off the Keychain Manager does not work. you must do the Export step. so once you follow these instructions and verify that your Keys are installed (in the Keychain Manager), relaunch XCode and you should now be able to select the profile in Project Settings.