I'm pleased to say that this problem was resolved.
We had inadvertently installed AIX 5.2 with a 32 bit kernel.
TSM was then installed with the non-matching 64 bit kernel components.
After re-installing with the 64 bit kernel, these library errors
went away.

>I've 'migrated' a TSM server from an F40 running AIX 4.3.3
>to a p615 running AIX 5.2.0.
>
>We are running TSM version 5.1.8.0 .
>This has been installed on the new machine.
>
>I copied across the dsmserv.dsk and dsmserv.opt files to
>the new machine, added tape & library devices again and
>restarted TSM on the new machine.
>
>The new machine is running in 64 bit mode so the code base won't be
>exactly the same.
>
>This is all worked OK apart from the fact that TSM appears unable
>to access the tape library controller.
>
>On start up, I get :
>
>031201-162646:  ANR8300E I/O error on library STKLIB (OP=00006C02, CC=207, 
>KEY=FF, ASC=FF,
>031201-162646:  ASCQ=FF,
>031201-162646:  SENSE=**NONE**,
>031201-162646:  Description=Device is not in a state capable of
>031201-162646:  performing request).  Refer to Appendix D in the 'Messages' 
>manual for
>031201-162646:  recommended action.
>
>I deleted the drive and library paths and the drive and library
>definitions within TSM. When I try to recreate the library path,
>I get :
>
>tsm: ADSM>define library stklib libt=scsi
>ANR8400I Library STKLIB defined.
>
>tsm: ADSM>define path ADSM STKLIB  srct=server destt=LIBRARY device=/dev/lb0
>ANR8418E DEFINE PATH: An I/O error occurred while accessing library STKLIB.
>ANS8001I Return code 15.

+----------------------------------------------------------------------+
 Steven Bridge     Systems Group, Information Systems, EISD
                          University College London