Oh yeah, right, I forgot: I am using Boost version 1.34.1 and gcc version 3.3.2, which is part of a toolchain for our embedded target system (and thus quite irreplaceable). Here’s the output xml file the before posted code generates: <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="4"> <ZMD120 class_id="0" tracking_level="0" version="1"> <px class_id="1" tracking_level="1" version="0" object_id="_0"> <TypeName>ZMD120</TypeName> <RequestedDataItems class_id="2" tracking_level="0" version="0"> <count>3</count> <item_version>0</item_version> <item>1.8.1</item> <item>1.8.2</item> <item>F.F</item> </RequestedDataItems> <SupportedProtocols class_id="3" tracking_level="0" version="1"> <px class_id="5" class_name="MeteringProtocolCompositeFactory" tracking_level="1" version="0" object_id="_1"> <IncludedProtocols class_id="6" tracking_level="0" version="0"> <count>1</count> <item_version>1</item_version> <item> <px class_id="7" class_name="Iec1107OverSerialFactory" tracking_level="1" version="0" object_id="_2"> <ProtocolFactory class_id="4" tracking_level="1" version="0" object_id="_3"></ProtocolFactory> </px> </item> </IncludedProtocols> <ProtocolFactory object_id="_4"></ProtocolFactory> </px> </SupportedProtocols> </px> </ZMD120> </boost_serialization> No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.17.11/1200 - Release Date: 27.12.2007 13:34