I’ve had this problem exporting from a local dev site to a live (staging) server. I have two web hosts – one running MySQL version 5.1(???) and another running 5.6.
The web host running 5.1 stalls at the ‘restoring database’ stage while the one running 5.6 has no problem.
I believe something changed in WP core during the recent 4.1 to 4.2 upgrade that altered the structure of the database and affected backwards compatibility.
To anyone having this problem it’s worth checking the version of MySQL running on the DB you’re exporting from and the DB you’re exporting to.