As reported by users of libcppa, the library fails to compile - or rather: to link - on the latest Ubuntu release with Boost. To get a running version of libcppa, please configure it using ./configure --standalone-build. This will disable the context-switching feature of libcppa. Context-switching is only relevant in case you want to have cooperative scheduling of blocking actors. When disabling this feature, all blocking actors are implicitly detached.
Since Boost only enables context-switching, we are considering to turn this feature into an opt-in rather than an opt-out at compile time. In case your system is lacking Boost, you won't get the context-switching actors anyways (and will not be affected by this error). Other parts of the library do not depend on Boost, so there is no degradation of performance or functionality.
If you run into a similar error on a different Linux distribution, please let me know.