I posted a bug on Mantis about this yesterday:
http://bugs.impara.de/bug_view_page.php?bug_id=0000501

Today I tried hard to find a reproducible scenario that makes Squeak
freeze. Although I reliably manage to freeze my image I was not
successful in finding a sequence of steps which does it all the time.
However, I post my findings anyway. Perhaps someone smarter than me can
figure out what is going on. Here is what I do:

1. Open Squeak3.8b-6351.
2. Open the SUnit Test Runner.
3. Deselect all.
4. Filter Stand*. This selects StandardSystemFontsTest.
5. Run All. The test fails.
6. Click on the failing
StandardSystemFontsTest>>#testRestoreDefaultFonts. This opens a
debugger.
7. Click Over. This opens a TestFailure.
8. Close it.
9. Close the first debugger as well. This reveals another debugger:
Unwind error during termination. See Unwind error.log.

I assume this is a bug and the first reason for the subsequent image
freeze. It may be a bug in my test case in my use of ensure:. Did I do
something wrong?

10. Click Proceed. (This debugger simply does not go away by Abandon or
closing.)
11. Goto step 6: Click the failing test again. Rinse and repeat.

Sometimes, not always I am afraid, my image freezes. There are three
scenarios for that:
- Either I get Error: Attempt to evaluate a block that is already being
evaluated. See Attempt to evaluate.log.
- Or I get MessageNotUnderstood: UndefinedObject>>resumptionTime. See
resumptionTime.log.
- Or it just freezes without a new debugger.

One more thing:
It looks to me that it might be so difficult to reproduce because there
are some timing issues. In some of my tests I waited some tens of
seconds between some of the steps and got the freeze.

Go figure! :(

It would be very interesting if anyone can reproduce this.

Probably, I am doing something that I should not do in the first place?
However, Squeak should not be freezable by just clicking around, should
it? ;-)

- Bernhard