No TTM57SL Output in MAC OS X Sound System Prefs

Hi Guys
Hope you can help.
Recently upgraded to 1.9.2 every thing was working fine yesterday.
Today I also made a change where I bought a USB drive, did a carbon copy of my internal hard disk so I have failover of my system should my internal HD die on me I can just switch to my USB2 Mac os image drive.
On checking serato when booting up from the USB2 drive I couldn't get any sound out. Checked the Sound menu in system prefs and ttm57sl wasn't listed. If I close Serato it appears, reopen serato is dissapears....
Running MBP unibody, 4gb, 2.4.
Can you please help, have a a gig next week.
Thanks in advance
Sam