If you were talking about trying to save changes to an "xref" dwg --
not a "block" -- I might be able to help you. If you're truly working
with a block, though, unfortunately I can't offer much help at this
time. (I would suspect, though, that the block was created without
floating properties made possible with BYLAYER and BYBLOCK settings.
You might also explore the ATTREDEF command but read up on it first,
using "Help", as it redefines a block and updates associated
attributes... while removing any format or property changes with the
ATTEDIT or EATTEDIT commands).
If, by chance, you're making changes to an "xref" drawing's layers
(freezing, changing colors, etc.) within a host/current drawing and
those changes aren't permanently saved within the host drawing's layer
table beyond one session (meaning when you re-open the host drawing it
has reverted back to the original xref-dependent layer settings), then
you need to look into a system variable called "VISRETAIN".
To make xref-dependent layer changes (made in the host/current
drawing) take precedence, type in "visretain" and set the value to
"1". Layer settings will then be saved with the current drawing's
layer table and persist from session to session.