Ahh, sorry; I thought you were specifying two different arguments. However, I get precisely no change in output when I put them in as you suggested. Very strange. I'm using g++ 3.3, for reference.

Fiddling around with otool doesn't reveal any way I can tell which version of the C standard libs my libraries were built with. I might be able to manually determine which library is linking in the dylib though.

Hah! Turns out there was a conflict with Quicktime 7.0.4. I'd initially discounted this as a possibility because Software Update informed me that my last installed version was 7.0.3, installed last November. But it turns out that 7.0.4 wormed its way in somehow on Feb 19th. One quick downgrade later, and I'm back in business. Excellent.

Thanks for the assistance, everyone. If nothing else, I'm a bit more familiar with libraries now.