The bug reporting system at http://llvm.org/bugs/enter_bug.cgi?product=clang guessed my operating system to be Macintosh, 9.x but it is Macintosh, 10.x. The form says to mail this address in case the system wasn't guessed right.
some details that are maybe helpful to you:
Mac OSX 10.4.11
Safari 3.1.2 (4525.22)
and I didn't do tricks to try to change my browsers user-agent.
Hope this is helpful to you!