3581 reconfigures and won't load next tape

Our 3581 tape unit isn't loading the next tape when it unloads a tape.  How do 
I fix this?

It used to auto load the next tape until I did two consecutive IPLs on Sunday.  
Peculiarly, after the second IPL, I couldn't vary on the tape unit because it 
was "in use by object TAPMLB04".  I had to vary off TAPMBL04 in order to vary 
on the 3581 (TAP01).

We also have another tape unit, a 3570 (TAP02).

A snip of QHST from the IPL shows:
Status of drive resource in device TAPMLB04 changed successfully.
Device TAP01 vary on failed.
Vary on completed for TAP02

Another peculiarity is that the 3581 auto configured from a 
TAPE UNIT 3580-002 00-0180XXXX TAP01  U0595.001.103093E-CB1-C07-T1L2-L0
to a
TAPE LIBRARY  3581-028   00-00000  TAPMLB04
after the IPLs.

Should I power cycle the 3581 in the hope that it will reconfigure back to a 
tape unit?  Will that cause it to load the next tape?

Thanks in advance.

Bryan Burns
ECHO, Inc.