Strange error using AS3 Library projects in FlashBuilder and command line ASC2.0

I'm getting a problem in ASC2.0.  The issue is intermittant.  I'm getting it using an AS3 Library Project.  Both FlashBuilder and the compiler via a command line say this:

Error: Can not resolve config constant: 'Default'

Error: Can not resolve config constant: 'Mobile'

I've tried to manually inject config constants and they seem to remove the error, but I'm not 100% sure I should be doing that, especially since I don't really know what values to set them to.  I used default=true and Mobile=false, but that scares me since I'm just guessing.

I look at the .actionscriptProperties, .flexLibProperties, and .project and couldn't find any mention of those constants.

The weird thing is that I have other AS3 Library projects which don't have this problem.  And it's a branch new project that's having the issue.

And like I said, it's intermittant.