A new version of Morphic was added to project The Inbox:
http://source.squeak.org/inbox/Morphic-dtl.634.mcz

==================== Summary ====================

Name: Morphic-dtl.634
Author: dtl
Time: 13 January 2013, 1:48:33.942 pm
UUID: 02716c40-7437-458c-80ff-22679fcd3c04
Ancestors: Morphic-dtl.633

Fix for Morphic layout bug reported by Bob Arning in http://lists.squeakfoundation.org/pipermail/squeak-dev/2013-January/167757.html

Invalidate changed regions in Morph>>layoutBounds: in the same manner as in Morph>>doLayoutIn:

=============== Diff against Morphic-dtl.633 ===============

Item was changed:
  ----- Method: Morph>>layoutBounds: (in category 'layout') -----
  layoutBounds: aRectangle
  	"Set the bounds for laying out children of the receiver.
  	Note: written so that #layoutBounds can be changed without touching this method"
+ 	| priorBounds outer inner box |
+ 	priorBounds := self outerBounds.
- 	| outer inner |
  	outer := self bounds.
  	inner := self layoutBounds.
  	bounds := aRectangle origin + (outer origin - inner origin) corner:
+ 				aRectangle corner + (outer corner - inner corner).
+ 	box := self outerBounds.
+ 	box = priorBounds 
+ 		ifFalse: [self invalidRect: (priorBounds quickMerge: box)]!
- 				aRectangle corner + (outer corner - inner corner).!