PST Migrator is freezing.

Hello.

I have recently upgrade from EV 7.5 to EV8 SP4 to EV 9. Previously, i had manually imported all user pst's into EV using the PST migrator, when we were on 7.5. Now I have a few more pst's to import. I launch the migrator and choose the appropriate vault store, but when I hit next, the wizard just hangs and never goes to the next screen. I've tried this on both of our EV servers. Any suggestions?