I upgraded to ImageMagick 6.3.6 last night and the nightmare of such things popped out: my scripts terminated suddenly with a "Segmentation fault". Ouch. On the other hand, the test suite for the Perl modules sort-of-worked, with some issues on a test file. So, it couldn't be *that* broken.
It ended up that it was a "coders" directory put somewhere, and in particular the ".so" library files that were in it. I don't really know anything about autoconf and libtool, but the most evident thing was that in the compiled directory there were two libraries for each file, one ending in ".so" and the other ending in ".soT", which was the one that got installed (and that caused the problem). And yes, the *dirty* hack to copy the original ".so" files over the broken ones worked.
I suspect that my compiling toolchain is a little dated... time to upgrade, I fear.