I am tearing my hair out over this, partly because I believe the code used to compile. I just can't see what the problem is. I enclose all the pertinent code as I cannot say which bits are irrelevant. There are two classes: ManagedArray which is an array of data without size or capacity data (this is stored elsewhere). PersistentManagedArray which I wrote to enable ManagedArrays to be serialized. The error message is produced in 'main': error: no match for 'operator<<' in 'oa << PersistentManagedArray<int>((* & size), (* & capacity), (* & ints))' It seems to me that I have defined the necessary serialize member function with the right signature. Commented out is code I wrote some time ago which used separate load and save functions. This, I believe, used to work. #include <fstream> #include #include #include <string> using namespace std; //**************************************************************************************************************************** template<class T> class ManagedArray { public: T *values; ManagedArray() { values = NULL; } ~ManagedArray() { if (values) { delete [] values; } } //Changes array size. If array grows, the new values are unintialized. void resize(unsigned oldSize, unsigned newSize) { if (oldSize==newSize) return; T *newValues = (newSize==0) ? NULL : new T[newSize]; if (oldSize!=0) { T *oldValue, *newValue; T *end = values + (oldSize