Since we upgraded from 2.4.10 to 2.6.5, some nodes crash randomly by segmentation fault (mongod.txt). On these nodes, the mongo shell won't start and do a segfault on startup (mongo-shell.txt).
We have tried to recompile mongodb with different versions of gcc or of the gilbc, which don't solve the problem. Same result when we disable all the compilation options (use-system-yaml, use-system-boost, use-system-pcre...).
The default compilation options are available in this ebuild : http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/dev-db/mongodb/mongodb-2.6.5.ebuild?view=markup

Other nodes have the same configuration, and mongo runs perfectly.