Hi guys. So we have a case where we can reproduce the problem. See http://code.google.com/p/pharo/issues/detail?id=6644
If you take a Pharo 20274 and load this slice: SLICE-Issue-6635-Removing-class-does-not-remove-class-tag-CamilloBruni.1 , the #testInstanceSideMethodsWithNilKeyInLastLiteral starts to fail and we have lots of instance side methods with nil in the last literal (in fact, from the package that the slide installs). I tried to debug the #basicLoad and MC friends to see if I come to the real problem but no luck so far. If anyone wants to take a look, it would be great since I think this is a really important bug. Thanks, -- Mariano http://marianopeck.wordpress.com