But I'm not building x64 application. That's the result of me troubleshooting, after win32 setup was not working.
The link2001 error occurs with win32 setup too. But the functions are somewhat different

Code:
1>------ Build started: Project: db64practice, Configuration: Release Win32 ------
02
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual struct pg_conn * __thiscall pqxx::connect_direct::do_startconnect(struct pg_conn *)" (?do_startconnect@connect_direct@pqxx@@UAEPAUpg_conn@@PAU3@@Z)
03
1>dbConnect.obj : error LNK2001: unresolved external symbol "protected: void __thiscall pqxx::connection_base::close(void)" (?close@connection_base@pqxx@@IAEXXZ)
04
1>dbConnect.obj : error LNK2001: unresolved external symbol "protected: void __thiscall pqxx::connection_base::init(void)" (?init@connection_base@pqxx@@IAEXXZ)
05
1>dbConnect.obj : error LNK2001: unresolved external symbol "protected: __thiscall pqxx::connection_base::connection_base(class pqxx::connectionpolicy &)" (??0connection_base@pqxx@@IAE@AAVconnectionpolicy@1@@Z)
06
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual bool __thiscall pqxx::connectionpolicy::is_ready(struct pg_conn *)const " (?is_ready@connectionpolicy@pqxx@@UBE_NPAUpg_conn@@@Z)
07
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual struct pg_conn * __thiscall pqxx::connectionpolicy::do_disconnect(struct pg_conn *)" (?do_disconnect@connectionpolicy@pqxx@@UAEPAUpg_conn@@PAU3@@Z)
08
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual struct pg_conn * __thiscall pqxx::connectionpolicy::do_dropconnect(struct pg_conn *)" (?do_dropconnect@connectionpolicy@pqxx@@UAEPAUpg_conn@@PAU3@@Z)
09
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual struct pg_conn * __thiscall pqxx::connectionpolicy::do_completeconnect(struct pg_conn *)" (?do_completeconnect@connectionpolicy@pqxx@@UAEPAUpg_conn@@PAU3@@Z)
10
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual __thiscall pqxx::connectionpolicy::~connectionpolicy(void)" (??1connectionpolicy@pqxx@@UAE@XZ)
11
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: __thiscall pqxx::connectionpolicy::connectionpolicy(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??0connectionpolicy@pqxx@@QAE@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)
12
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: virtual __thiscall pqxx::errorhandler::~errorhandler(void)" (??1errorhandler@pqxx@@UAE@XZ)
13
1>dbConnect.obj : error LNK2001: unresolved external symbol "public: __thiscall pqxx::errorhandler::errorhandler(class pqxx::connection_base &)" (??0errorhandler@pqxx@@QAE@AAVconnection_base@1@@Z)
14
1>f:\visual studio 2010\Projects\db64practice\Release\db64practice.exe : fatal error LNK1120: 12 unresolved externals