MT song playback ok, playlist not ok

OK,
so I’ve just flashed FW V-83859 (the old one was V-8487) and LP-16 is UNUSABLE :angry:

I used exactly this file “LivePlayer_LP-16_Firmware_Upgrade_83859_x64.exe” (I’m on Windows 7 64bit).
Everything worked great, I got a message saying the firmware had been upgraded – “Upgrade successfully finished”.

Now when I connect my USB flash disk, LP-16 tells me “MT USB device test – Please wait”,
then it says “MT TEST passed, USB flash drive, free space: xxx GB”.
Then the main MT screen shows up, showing “Song 1 of 15” etc.
Then after approx. 4 seconds everything repeats (MT USB test, test OK, main MT screen) again and again…. until I switch it off.
No button is working!

I tried to re-flash FW once again but the result is the same.

EDIT:
I formatted my USB flash drive to NTFS and LP-16 indeed offered me to format it for using it with LP-16.
I was able to press PLAY to format it. After formatting everything stays the same: LP-16 detects USB flash, passes the test and shows “No songs found” and then again the detection procedure, etc…