Windows 7 x64
Blender 2.77 windows 64
When packing into zip a blendfile through the blender UI (not in "background"), there's an import error.
I guess it's in blendfile_path_walker.py (in the blend folder) at line 630
I just replaced "import blendfile" by "from blend import blendfile" and it worked.
Exact steps for others to reproduce the error
Open blender with the default scene, activate the blendutils addon.
Click on File/External Data/Pack Blend To Archive.