This problem only occurs with Visual Studio 2003. (The solution is described below) It does not occur with Visual Studio 2002, 2005, or 2008.
Your application will get an unresolved external error message if it tries to use any Chilkat method involving wchar_t, such as:
MfcLinkTest error LNK2019: unresolved external symbol "public: wchar_t const * __thiscall CkString::getUnicode(void)const " (?getUnicode@CkString@@QBEPB_WXZ) referenced in function "public: __thiscall CMainFrame::CMainFrame(void)" (??0CMainFrame@@QAE@XZ)
Open the Project/Properties and select the "C/C++" tab. Then select the "Language" sub-category. The "Treat wchar_t as Built-in Type" property defaults to "Yes". This should be changed to "No".
Setting the "Treat wchar_t as Built-in Type" project property equal to "No" solves the unresolved external problem.