What kind of HBA are you using in the client machine ?
What is the tape library ?

Has LAN-free ever worked on this node, or has it just gone wrong recently ?

If you say the backups are now going to a disk pool, then the mgnt class for
those files are not pointed at a tape pool.  Apart from the drive mappings,
you have to point the the LAN-free client at a stg pool that is accessable
directly over the SAN.  ie the tape or a SANergy disk pool.

If you are using a Qlogic HBA in Windows 2000,  sometimes new machines
entering the SAN fabric can change the device name the ADSMSCSI driver see
the tapes as.  Check the "mtx.x.x.x" names on the stg agent machine are the
same as you have mapped.  Also with Qlogic, W2k can lose sight of the tape
drives if other machines are rebooted on the SAN.

Lastly if you started the stg agent, then defined all the drive maps to it,
I've seen that the stg agent doesn't always pick this up right away.  Try
stop/starting the stg agent to pick up the mapping conf.

Jason