I've seen this happen alot.
When booting up after external media identifier runs on the progress_window the screen clears to only showing green bars (no text).
I've let the system sit for 20 minutes with no change.
<CTRL/ALT> F1 on MD shows
Not starting device 41 External Media Identifier - binary "External_Media_Identifier" is not found.
I've had this happen on Core and both MD's.
It is not consistent.
<CTRL/ALT> F7 provides main menu screen.