I finally checked what actually had changed in the plugin code and I found that it was unrelated to inlining. The only change was the declaration of two constants as U instead of ULL[1]. So, I decided to add the correct type declarations and recompiled the plugin, which seems to work for me; the image-side tests pass. Unfortunately, I don't have access to the Cryptography repository, so I uploaded the changes to my place[2].
Levente
[1] http://squeakvm.org/cgi-bin/viewvc.cgi/squeak/branches/Cog/src/plugins/DSAPr... [2] http://leves.web.elte.hu/squeak/CryptographyPlugins-ul.11.mcz