Yes. I just tried encfs and have the same problem.
Found this bugreport which has more info about the problem:
http://code.google.com/p/encfs/issues/detail?id=60
It seems the boost guys changed something about serialization in 1.4.2.
Im back to 1.4.1 now, that works for me.
I used the slackbuild for boost from slackware-current/source/l/boost, works
without changes for 1.4.1 and then added boost to my slackpkg blacklist ...
After that you probably have to recompile encfs because of shared library error