Appreciate your reply. I'm not sure I'm getting anywhere!
I booted up using a Guest user account and at first all was well, Toast launched few times(maybe 6) then refused to launch completely.
I went back to my main user account, same thing - refused to launch repeatedly. Next I disconnected everything non Apple (3 external USB drives and four audio interfaces using FireWire) and booted up again.
Hey presto! Toast launched ok.
So I remounted each drive(verifying with Disc Utility that each drive was ok), then switched the audio interfaces on again. I did this one device at a time checking that Toast launched ok each time. At the end of this everything was connected again, and Toast was ok. However, a restart with everything connected was followed by repeated refusal of Toast to launch.
At the moment I am finding that my audio interfaces do effect whether Toast will launch or not!
Sometimes, I can switch one of the four interfaces off and Toast will then launch, but it's not always the same one! Sometimes after a successful launch of Toast with one interface off, switching it on again does not cause it to fail to launch. It's all inconsistent; but a restart nearly always causes problems! I should say that once Toast has launched ok, it doesn't seem to crash - it's always on LAUNCH that there's a problem with a failure report generated like the one I sent you. The SIGBUS line is always the same though.
Not sure what's next......