Boot problem: stuck

[mahesh]

Running ubuntu 20.04 from usb ssd vx500, today morning the Boot process halted with these lines:

ACPI Error Needed type Reference...
ACPI Error AE AML operand type..
ACPI Error Aborting method PR.CPU0 PDC...
Blacklist Problem blacklisting g hash -13
5x
/dev/sda2: clean ...
Bluetooth hci0 unexpected event formopcode 0c0000

What can I do?