Hi! After several days of surfing the beatiful ImageSegment code, I fixed several issues. I commit to Inbox the SLICE-FixesToImageSegment. This are the changes in my commit: - Removed Beeper beepPrimitive from ImageSegment >> install - Fix to writeToFile. See issue 1204 http://code.google.com/p/pharo/issues/detail?id=1204 - Now ImageSegment >> discoverActiveClasses answer the number of them - New method ImageSegment >> unActiveClasses - Fix to ImageSegment >> swapOutInactiveClasses. I have to hold the allSymbols and to exclude the Multilingual and Kernel package from the swap. This should fix issues 1203 and 1204. - The errors for wrong states now print the current state and also the expected one. - Fix issue 207. Take a clean image and evaluate: Smalltalk at: #MDFaultDict put: Dictionary new. Then | count | count := ImageSegment discoverActiveClasses. Transcript show: 'Classes forced: ', count asString. Do something And finally evaluate | count | count := ImageSegment activeClasses size. Transcript show: 'Classes active ', count asString. or | count | count := ImageSegment unActiveClasses size. Transcript show: 'Classes active ', count asString. Whit this, there is no trace. Even if puting the dictionary. A simple hack to see this is to change activeClasses to use recoverFromMDFaultWithTrace instead of recoverFromMDFault If you do that, you will be able to inspect Smalltalk at: #MDFaultDict I also fixed the swapOutInactiveClasses. The image have several emergency windows before this.