Hi Charlie, Our Chimera 1.2186 snapshot was compiled on Mac OS 10.4 and will not work on Mac OS 10.3 or earlier OS versions. Our Chimera 1.2184 release was compiled on Mac OS 10.2 and works on Mac OS 10.2, 10.3 and 10.4.2. It does not work on Mac OS 10.4.3 because of a C++ exception that we are still trying to figure out. If you compile a Python module on Mac OS 10.3 using our Mac OS 10.2 compiled Chimera you may run into compiler incompatibilities since 10.2 and 10.3 use different versions of gcc. If your module uses any C++ code there will almost certainly be incompatibility. My guess is that your problem is somehow related to this. I just put the Chimera 1.2184 headers files for Mac on our web site. Maybe that is the problem since you used 1.2183 headers to build against our 1.2184 Chimera. But I don't think this is the problem. It may be that the only solution is for you to compile your module on Mac OS 10.2, or for us to provide a Mac OS 10.3 build of Chimera. We are working on bringing some sanity to the multiple flavors of Chimera on Mac OS. We do not have a single version that works on 10.4.3 and earlier Mac OS versions. And we are looking ahead to how we will support Intel Macs. And we would like to try (again) an Aqua version of Chimera (no X windows). Tom