There were three incarnations of the beast : one active, one same model underneath it , plus one in storeroom (old ibm) so unless that has been "cleaned-up" you should be able to go back to that.
I know Nortel / BT don't support MAT any more, but last ditch option would be check revision level in either Drieiech or Paris & compare, then do a search for any missing patches.
I might be able to help on that front if you get stuck.
<Do I need A Signature or will an X do?>