Building with XCode

I'm having a couple of problems building with XCode. For starters, when I downloaded the source, most of the files had a modified date of July 20, 2006, which caused the XCode compiler to rebuild from scratch everytime I wanted to build the project. I have since then set all the C++ header and source files's modification date to July 15, 2006 so that it will only rebuild changed files from now on. However, it does not seem to honor my changes to the target architectures in the projects configuration settings. No matter what I select, the debug build comes out as an Intel-only application. At one point I think it was building as Universal (when both Intel and PPC were selected), but now it will only build to Intel no matter what I do. I would never build as a PPC-only app, which is what I was originally trying to do.

Has anyone else had these problems with building in XCode? Or has something really obscure occured on my system to create these errors? Any recommendations?

FYI- My system is a 2.0 Intel Duo iMac with the latest version of Mac OS X. Its a less than one week old sytstem, and everything has been fully updated, as near as I can tell.