Hi folks! I having this problem in pharo1.0-10496-rc1dev09.11.4 but I cannot reproduce it in PharoCore-1.1-11078-ALPHA I don't think it is because of the Pharo version but becuase of dev/core. I would like to tested in a dev from 11078 but the last one I tested was not working as I have warings and popups everywhere (there is already a thread for that). I am in Mac OS. Anyway, you can reproduce it in a fresh pharo1.0-10496-rc1dev09.11.4 image. Steps to reproduce: 1) Download from http://www.squeaksource.com/JBARepo the package VMMakerLoader 2) Evaluate "VMMakerLoader loadAndFix" 3) Browse the class Interpreter 4) Go to the method primitiveStoreImageSegment. Click on the method and after a second you will have this error. I attach PharoDebug.log in the issue tracker: http://code.google.com/p/pharo/issues/detail?id=1559 Cheers, Mariano