> that seem sto be related to a broken Debian patch within the 45.x > releases. Christoph figgured this out and hopefully with the next > version 45.2.0 this should be fixed. The new icedove package (1:45.2.0-2~deb7u1) in Wheezy LTS does have the problem Cédric described. However the previous one (1:45.1.0-1~deb7u1) didn't.
A workaround for us was using a mozilla.cfg in /usr/lib/icedove and putting all lockPref in there. 'pref("general.config.filename", "mozilla.cfg");' and 'pref("general.config.obscure_value", 0);' might be set as well in a .js config.