You should be using the "Debug Multithreaded DLL" compiler option in your application when you link with the build_win32/Debug/libdb.lib library (this .lib file is actually a stub for libdb.DLL). To check this setting in Visual C++, choose the "Project/Settings" menu item, and under the tab marked "C/C++", select "Code Generation" and see the box marked "Use runtime library". This should be set to "Debug Multithreaded DLL". If your application is linked against the static library, build_win32/Debug/libdbs.lib, then you will want to set "Use runtime library" to "Debug Multithreaded".
Setting this option incorrectly can cause multiple versions of the standard libraries to be linked into your application (one on behalf of your application, and one on behalf of the Berkeley DB library). That violates assumptions made by these libraries, and traps can result.