I'm running ubuntu studio, 16.04, XFCE with Thunar. After some updates this week, the Filemanager hangs for a fair while - over a minute possibly.
When a window does appear, it picks up my network mounted drives but it won't pick up any USB drives.
Running df at the command line also hangs.
Edit: As suggested, I installed another File Manager - Nemo - which exhibited the same problems as Thunar.
I think the problem is with the back-end systems. I'll wait for an update.
Edit 2: And with an update, it's up and running. Cheers.