The issue is likely that because you have a DLL importing symbols from another DLL, and that all of the symbols are being marked for export as du[DE] explained above.
What you need are conditional declarations dependant on each DLL, so that they won't be mistakenly interpreted incorrectly by other DLLs.
Modify your header to look something like this.
#ifdef DLLTEST1_EXPORTS
#define DLLTEST1_API __declspec(dllexport)
#else
#define DLLTEST1_API __declspec(dllimport)
#endif
class DLLTEST1_API CTest1 {
public:
CTest1(void);
};
Then define DLLTEST1_EXPORTS in either your Test1 project or in the stdafx.h for that project.