Problem updating image to latest

When I try to update my image, I eventually get a debugger window with various different DNU situations triggered by a displayWorld call.  In each case, the receiver that triggers the DNU is not the value it should be (or that the debugger says the value is).  For example, the top of the debugger stack:

SmallInteger(Object) >> doesNotUnderstand: #isEmptyOrNil
PluggableListMorphOfMany(PluggableListMorph) >> hasFilter

where:

hasFilter
        ^ lastKeystrokes isEmptyOrNil not

the debugger in the context of hasFilter says that lastKeystrokes is an empty ByteString, but when I click on self for the SmallInteger DNU, it says that the receiver is a SmallInteger 0.

This happened during the update at “Processing update-ul.303.mcm” / “Reshaping Morphic-mt.824”, but I’ve also seen it fail more catastrophically later on when a message send to BorderStyle class actually sends width:color: to the ByteString #simple, causing every window to eventually be drawn with the

I am running with the following Image and VM config:

Image
-----
/Users/tim/Programming/Squeak4/Squeak4.5.image
Squeak4.4
latest update: #14301
Current Change Set: Morphic-mt.824
Image format 6505 (32 bit)

Virtual Machine
---------------
/Users/tim/Programming/Squeak4/Cog.app/Contents/MacOS/Squeak
Croquet Closure Cog VM [CoInterpreterPrimitives VMMaker.oscog-eem.1288] Squeak Cog 4.0.3319
Mac OS X built on May  6 2015 15:44:21 UTC Compiler: 4.2.1 (Apple Inc. build 5666) (dot 3)
platform sources revision VM: r3319 http://www.squeakvm.org/svn/squeak/branches/Cog Date: 2015-05-05 22:28:32 -0700 Plugins: r3275 http://squeakvm.org/svn/squeak/trunk/platforms/Cross/plugins
CoInterpreter VMMaker.oscog-eem.1288 uuid: 909625f0-4d63-4a3b-84e1-1f2753923d7e May  6 2015
StackToRegisterMappingCogit VMMaker.oscog-eem.1288 uuid: 909625f0-4d63-4a3b-84e1-1f2753923d7e May  6 2015


I downloaded the latest VM just today, but this was failing on the previous Cog VM, as well.  Also, my original image seems to run fine with both VMs, so it appears to be something in the update process that is causing the problem.  Any ideas on how to debug this further?

        — tim

Update:

I now think the problem is in the Cog VM:  I downloaded a clean image from Squeak.org and ran into the same problems (simply opening a Preferences Browser and clicking on the first item in the list will trigger a DNU).

Running my current image with an older interpreter VM (Squeak 5.7.4.1) shows no problems.

        — tim