error 65, works in Xcode

Background:

I dabbled in Obj-C two years ago and mean to get back to it this summer.  Just finished teaching a course in software development and for the course project, one of my student asked if he could develop it for his iphone (he seems to do a lot of development in iOS) instead of Java; I said okay.  I get his project and tested it in xcode, ran correctly.  In the meantime, I was searching for comments on xcode and discovered AppCode.  I got the trial version and tried running his app on it.

When performing run, I get the following errors:

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2013-05-07 09:54:46.758 xcodebuild[5192:707] WARNING: skipping plug-in at path '/Users/xxxxxx/Library/Application Support/Developer/Shared/Xcode/Plug-ins/XcodeAutoAssistant.pbplugin' because it is not compatible with this version of Xcode.

Code Sign error: The identity 'iPhone Developer' doesn't match any valid, non-expired certificate/private key pair in your keychains

The following build commands failed:
Check dependencies
Build Finished with Error: 65
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I have the latest xcode installed, no additional apps except AppCode.  I don't understand why something is not compatible with "this version of Xcode" - is the problem with AppCode?  Any input would be appreciated.  I searched for error 65, but turned up a lot of posts here that seem generic or relate to many different types of problems.

Thanks.