Hi,
I had the same problem recently, being stuck at the scanning stage. It happened suddenly on all my websites, on several websites on different hosts.
I partially solved it by downgrading to duplicator 0.5.2
without any other changes, it worked for me.
note :
all websites were on wordpress 3.9.1 – in french. I tried deactivating other plugins or toying with file permissions with no luck.
Maybe you can give it a shot. it takes 2 minutes to downgrade and test.
Regards,