Crash dump gives driver unavailable

Hi

When analyzing a crash dump, I am determining running driver information by
a
?!drivers? command returns some drivers, and mine in particular,
as:

bf0cb000 0 ( 0 k) 0 ( 0 k) XYZ.sys unavailable

Anyone care to shed any light on why or what this indicates? I know it must
be loaded
and running.

Thanks
Steve