Thanks for the replies guys. Initially I thought this was an extension conflict but even restarting with various known safe/or 'None' combos is giving some random results...the latest is the mouse click has suddenly become "inverted"- it is always "clicking" with no button push, to release/de-select whatever the mouse has bound to, it is necessary to hold the button down while moving the mouse.
(Previously I had Rebirth, Reason and Logic 6.4 all working flawlessly, synched to my current OS X DAW using OMS...)
btw, disk utility reported/repaired errors, but not much changed- would an OS9 re-install be the next step?