Hi Boosters, I had the compile time warning discussed here ( http://boost.2283326.n4.nabble.com/Serialization-C4308-warning-with-MSVC9-td...) that Robert is probably fed up discussing. I've read for months, but didn't want to const_cast my object (or is it ok sometimes?). However, making my destructor virtual removed the warning. Here's my question: why does making the object destructor virtual remove the warning, effectively making my object instances const? And the section on this trap from the Rationale section of the Serialization documentation is not in the1.47 version (howcome?) but can be found in previous version here: http://www.boost.org/doc/libs/1_39_0/libs/serialization/doc/rationale.html#t... Oh, and please forgive me if the answer is *obvious* - just an intermediate programmer. Colin