While debugging FloatTest>>#testNaNCompare (From 
http://bugs.squeak.org/view.php?id=6719 FloatNaNCompare-M6719-Test.2.cs),

I had a very strange behavior:
Executing in Debugger:

	theNaN := Float nan.
	anotherNaN := Float infinity - Float infinity.
	comparand := {1. 2.3. Float infinity. 2/3. 1.25s2. 2 raisedTo: 50}.
	comparand := comparand , (comparand collect: [:e | e negated]).
	comparand := comparand , {theNaN. anotherNaN}.

I ended up with a comparand filled with some nils.
The problem vanished when I did recompile.

Unfortunately I saved the image before I had the idea to inspect the 
Bytecode and then could not reproduce the problem.

I suspect it is related to http://bugs.squeak.org/view.php?id=6720 .
Does anyone experiment this kind of problem?

Nicolas