Regards Rick from New Zealand
That is a supported format, and this is a bug. Deactivate Premiere Pro (in the Help menu), uninstall it, and then run the Adobe Creative Suite Cleaner Tool. After you run it once, reboot, and then run it again--that makes sure you get rid of everything. After a final reboot, reinstall Premiere Pro and reactivate; it should work this time.
It's a big, annoying bug that Adobe can't seem to shake, and why it happens appears to be random and without clear cause.