Sorted. But i was too chicken to try the Terminal fix n7smith kindly pointed me to. Thanks n6smith anyway. Greatly appreciated. Luckily, as i said, i'm paranoid about archiving so i ended up replacing the External Drive that initially caused the crash using its clone. Nothing wrong with the drive itself but it was an incompatibility issue with an Energy Saver Drive, the enclosure it was in, and the way Ivory wanted it to behave. Gave me no end of grief so this was the impetus to sort it. I also bought a faster 2.5" drive, did a Time Machine restore to it, then installed it in my Mac Mini. A few issues but nothing that won't get fixed a small problem at a time over the next few days
So this is a long winded post to say thanks for the help, and saying thank God (or Steve Jobs) for Time Machine!
Logic Pro 10.0.1, Mac OS 10.8.4
Mac Mini Lion Server - 16GB Ram - 480GB SSD
Focusrite Liquid Saffire 56
Stylus RMX, Trilian, Omnisphere, Komplete 8 Ultimate, Ivory Uprights, Ivory II Grands, Superior Drummer