Try to convert VSS 6.0 to SVN with this tool VSSMigrate. I got following Error.
System.InvalidCastException: Unable to cast COM object of type 'SourceSafeTypeLib.VSSDatabaseClass' to interface type 'SourceSafeTypeLib.IVSSDatabase'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{2A0DE0EE-2E9F-11D0-9236-00AA00A1EB95}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)). at SourceSafeTypeLib.VSSDatabaseClass.Open(String SrcSafeIni, String Username, String Password)
What i Know for this error is current migration tool can't support VSS 6.0 and only support VSS 2005. So, Is there any other tools to Migrate VSS 6.0 to SVN