[Aussie Mick]

Yes have gone one step furthere than trashing the preference.
I have put a new 500Gb drive in with a new stystem 10.5.5. and tried 10.5.6 as well.
I only loaded the Pro Tools 8 plus the cs8.3 software and my 2 Midi I/O's nothing else on my Mac.
I then went into AMS and sent my Midi I/O devices from scratch.
Restarted my MacPro and there it was, 1 of my Midi I/O's in grey and a new one put in it's place with no of me midi devices on it.
I own 2 Midi I/O's so I have been able to A B them. Nothing wrong with the devices and yes I have updated the firmware to version 2 in both Midi I/O's many times.
I have also striped my Mac down so there is no USB devices or any thing else hanging off it except my HD cards and my 192's with my Sync I/O interfaces.
I must piont out that I never had any trouble with my PowerMac running Pro Tools 7.4.x
We have played enough games now so we need to have this problem escalated to the code writers or tech heads.
Also I have a MOTU 128 express Midi device and it work every time.