Thanks for that tip. I did buy FontDoctor and run it, not sure how successfully.
I sent a file which I was having major crash problems on to tech support. It crashed for them too under OS 10.6 but worked under OS 10.5.
However Apple tell me that OS 10.6.2 is 'hard-wired' into my iMac and so I cannot go back!
I decided to do some expeiments on my own. I created two NEW files both containing the identical text one using a system font–Geneva–and the other using a Type1 font Sabon which is used in a document which is also causing me problems.
I tried a lot of different operations on both files including a search and replace operation that had more than 55,000 instances. It took a while but neither file crashed under any of the tests.
I also managed to copy text from an old file and paste it into a NEW document I created. In the old file when I went to 'check usage' it crashed in the new one no crash. I pasted the text checked usage and it did not crash. I performed multiple operations on the new file and it did not crash either.
So my insight, which I am quite happy to have proved wrong, suggests to me that it is not just a Type 1 issue but it also seems to be linked to 'legacy' files. I have not done exhaustive testing, but any file I have created in v8.15 from scratch seems to work but older files opened in v8.15 do have problems.