I have a little app that downloads stock prices and was working perfectly (for years) until my recent upgrade to 10.5.7. After the upgrade, the program would crash on this
I'd suggest not using synchronous URL connections. It does require some code restructuring, but it's really bad behaviour to block the main thread on network. (Assuming you're doing this in the main thread).
Also, I'm guessing it's code that Apple is planning to deprecate or stop maintaining, which might be what you're seeing here.
Hope that helps….