Problems with std::locale when upgrading form 3.3.6 to 3.4.6

[Pep]

Our code used to compile happily under g++ 3.3.6 but now that we have
 upgraded the compiler to version 3.4.6 our code breaks when linking
 with this error message

undefined reference to `std::locale::id::id()

Can anyone tell me why and what the solution is?

I have been ploughing through the g++ 3.4.6 release notes to correct
 template problems and now do not know where to look having come across

 this problem :( 
 
TIA, 
 Pep.