Ok, here is the last section of the install log. It looks like it got a hpet runtime error.
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Parsing completed
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Disassembly completed, written to "dsdt.dsl"
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: ./patcher.rb:264:in `patch_hpet': No HPET Device found (RuntimeError)
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./patcher.rb:189:in `patch'
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./patcher.rb:219:in `verbose'
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./patcher.rb:189:in `patch'
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./patcher.rb:184:in `patch'
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./patcher.rb:344
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./installer.rb:6:in `require'
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from ./installer.rb:6
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall:12:in `require'
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: from /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall:12
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]:
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Intel ACPI Component Architecture
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: AML Disassembler version 20080926 [Oct 4 2008]
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Copyright © 2000 - 2008 Intel Corporation
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Supports ACPI Specification Revision 3.0a
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]:
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Handling RTC Device...
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Patched!
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Handling RTC Device done
Sep 6 18:33:08 xx-mac-pro /Volumes/Snow/private/tmp/scripts.8gSN/./postinstall[1315]: Handling HPET Device...
Sep 6 18:33:08 xx-mac-pro Installer[1304]: Install failed: The following install step failed: run postinstall script for snowjob. Contact the software manufacturer for assistance.
Sep 6 18:33:09 xx-mac-pro Installer[1304]: IFDInstallController 85B590 state = 7
Sep 6 18:33:09 xx-mac-pro Installer[1304]: Displaying 'Install Failed' UI.
Sep 6 18:33:09 xx-mac-pro Installer[1304]: 'Install Failed' UI displayed message:'The following install step failed: run postinstall script for snowjob. Contact the software manufacturer for assistance.'.