I'm writing a program in VC++ 6.0 professional and am encoutering a baffling error. The program compiles fine, but seems to be fed up with anymore member functions. If I add one in the header implementation it still compiles but if I call that function anywhere in the program I get:

Creating library Debug/ConflexCPP.lib and object Debug/ConflexCPP.exp
ConflexDlg.obj : error LNK2001: unresolved external symbol "public: void __thiscall CConflexDlg::thing(void)" (?thing@CConflexDlg@@QAEXXZ)
Debug/ConflexCPP.dll : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

I'm creating an ATL simple control in an existing application but I'm sure this is purely a C++ error. Any ideas?