Hi Robert, It's not all that clear from the documentation what one can expect of the versioning scheme in Boost.Serialization. It would seem (and correct me if I'm mistaken): (1) Archives created with *older* versions of Boost are not guaranteed to be readable in *newer* versions of Boost (as the OP has discovered). (2) Conversely, there is no mechanism by which archives created with a *newer* Boost version can be guaranteed to be readable by a specific *older* version of Boost. Consequently: (3) It is not generally possible to write a program capable of reading archives that have been written by multiple distinct versions of itself. (4) It is not generally possible to write a program capable of writing archives that will be readable by multiple distinct versions of itself. Regardless of whether one thinks these issues are serious or not, I think they should at least be prominently documented, as the potential for pain is quite high. Essentially, the current versioning scheme can make it prohibitively difficult to ever upgrade the version of Boost that a particular codebase is using. Regards, Jarl.