I have Mac OS X 10.5 (Intel). I already have X11 installed.
I have the same problem as the others.
The GIMP icon just bounces on the dock and then disappears.
Below are the problem details. thanks!
Process: gimp-2.4 
Code Type: X86 (Native)
Parent Process: sh 
Date/Time: 2008-07-05 05:57:08.263 +0800
OS Version: Mac OS X 10.5 (9A3115a)
Report Version: 6
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000
Crashed Thread: 0
Dyld Error Message:
Library not loaded: /usr/X11/lib/libXrandr.2.dylib
Referenced from: /tmp/skl/Gimp.app/Contents/Resources/lib/libgtk-x11-2.0.0.dylib
Reason: Incompatible library version: libgtk-x11-2.0.0.dylib requires version 4.0.0 or later, but libXrandr.2.dylib provides version 3.0.0
I can read the Reason there but I have no idea how to fix it. I just recently replaced a PC with a Mac so I have no idea yet how to do
things using this OS.