Finder Cover Flow Icon Preview not working
hm. Removing my answer, because not helped.

So - you got a message into Console.log. So, come step-by-step. :)

What return this command?

lipo -detailed_info /System/Library/Frameworks/QuickLook.framework/Resources/quicklookd.app/Contents/MacOS/quicklookd


Should this:

Fat header in: /System/Library/Frameworks/QuickLook.framework/Resources/quicklookd.app/Contents/MacOS/quicklookd
fat_magic 0xcafebabe
nfat_arch 2
architecture x86_64
    cputype CPU_TYPE_X86_64
    cpusubtype CPU_SUBTYPE_X86_64_ALL
    offset 4096
    size 504912
    align 2^12 (4096)
architecture i386
    cputype CPU_TYPE_I386
    cpusubtype CPU_SUBTYPE_I386_ALL
    offset 512000
    size 399280
    align 2^12 (4096)