Sony MVC-FD97 Operating Instructions (primary manual) Operating Instructions Manual page 86

Message
INVALID OPERATION
for "InfoLITHIUM" battery only
-
86
Meaning
You are playing back a file that was
created on equipment other than your
camera.
The battery is not the "InfoLITHIUM" type.
The image is protected.
The battery level is too low. When the
remaining time is about 5 to 10 minutes,
E
may flash depending on the battery
pack used, operating conditions, or the
environment.