Since you have the libICE.dll in place, I am really puzzled now.
Checking the version of the Xfree package, mine is 4.3.0.1.
But since you installed a new release, this is certainly ok.
I go with Rich Hammet: If everything else fails, bunzip2 (installed with cygwin) the XFree86-bin-4.3.0-1.tar.bz2 file in the release\XFree86\XFree86-bin folder of your cygwin download folder. then open (either use the tar -xvf XFree86-bin-4.3.0-1.tar, or simply use WinZip) it and put the missing files into the C:\cygwin\usr\X11R6\bin folder.
