I'm guessing here, but I think this was a reference to the fact
that in 10.5, Apple did some work to make X11 start automatically
when the first X11 app is run; maybe that's not working for pietro.

Is everyone having a problem on OS X on 10.5? I am.

OS X doesn't have strace; ≤10.4 has ktrace, 10.5 has dtrace.