Dear all,

Thanks for your replies. It turned out it wasn't due to a zombie pointer, though I did turn on that setting to check (hadn't thought of that as a possibility for this problem).

After quite a lot more poking around (much of it irrelevant in the end!) I realised that it was all down to the fact that under these specific circumstances the offending call to unlockFocus in my code was not preceded by a call to lockFocus. Fixing that bug has solved the problem! I think I was thrown off by the fact that this was only happening on one system and not reproducible on others - which, along with the ultimate crash being in private classes that I was struggling to find information on, primed me to think it was some sort of version-related issue.

Cheers
Jonny.