Richard reminded me he wrote on this subject a few years back. Enjoy. Below is the money quote:
[W]hat I am asserting here is not that Christianity alone is responsible for the Dark Ages. I find Christianity to be a symptom, not a cause, of the fall of the Roman Empire and the ideals it founded or fought over (see my discussion The Rise of World Christianity). What I am saying, however, is that Christianity didn't do any good. It neither corrected what had gone wrong nor reintroduced any striving for the dreams and aspirations of earlier Greek and Roman idealists, but to the contrary, Christianity embraced a partial and sometimes full retreat from them. Hence Christianity did not kill science. But it made no effort to rescue and revive its ideals, and instead let them drown, with little sign of regret, and in some cases even to praises of its demise. Thus, Christianity was bad for science. It put a stop to scientific progress for a thousand years, and even after that it made science's recovery difficult, painful, and slow.