I ran into a problem for a Windows hosted Plone setup where zeopack.exe failed because the blob_dir has weird characters in it.
I assume this is happening because of file encoding and windows.
What I did to overcome this was to pass in the blostorage dir via commandline:
zeopack.exe -B C:/Plone4/var/blobstorage
Refs http://plone.293351.n2.nabble.com/Zeopack-Error-123-td7402630.html