SAFESESH IMAGE/LNK2019: unresolved external symbol (Help a Newbie)

I'm newbie at programming and I'm trying to learn somethings, I've had a problem with SAFESESH IMAGE and I've found out that probably my libs are outdated and If I turn it down, the errors dismisses. So, after resolving many errors displayed by MSVB 2013 I'm stuck at this "supposed" last one error.

Error 38 error LNK2019: unresolved external symbol "__declspec(dllimport) class std::basic_string,class std::allocator > __cdecl std::operator+,class std::allocator >(class std::basic_string,class std::allocator > const &,char)" (__imp_??$?HDU?$char_traits@D@std@@V?$allocator@D@1@@std@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@0@ABV10@D@Z) referenced in function "public: virtual bool __thiscall glictTextbox::CastEvent(enum glictEvents,void *,long,void *)" (?CastEvent@glictTextbox@@UAE_NW4glictEvents@@PAXJ1@Z)

This is the lib = GLICT_mt.lib(textbox.obj)

After trying to understand this erros, I suppose that the error is in the function file "textbox.h" that's included in many other files of the project. But, I don't know if the error's caused by old libs or by an old writed function.

This is the file "textbox.h"

/*
    GLICT - Graphics Library Interface Creation Toolkit
    Copyright (C) 2006-2007 OBJECT Networks

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/**
 * \file textbox.h
 * \brief Textbox
 * \sa glictTextbox
 */

#ifndef __GLICT_TEXTBOX_H
#define __GLICT_TEXTBOX_H

#include <GLICT/container.h>
#include <GLICT/types.h>

/** \brief Rectangle shaped area that accepts keypress events and changes its
  * own caption accordingly.
  *
  * Rectangle shaped area that accepts keypress events and changes its own
  * caption accordingly. If it contains focus, an underscore character is
  * appended. No scrolling (meaning PalmOS style.)
  *
  * \todo If textcursor goes out of bounds of textbox, scroll the text
  *       appropriatelly to follow the cursor
  */
class glictTextbox : public glictContainer {
    public:
        glictTextbox();
        ~glictTextbox();

        void SetBGColor(float r, float g, float b, float a);

        // redefined functions
        void Paint();
        bool CastEvent(glictEvents evt, void* wparam, long lparam, void* returnvalue);


                void SetPassProtectCharacter(char asterisk); ///< Used to define which character will be used to display instead of regular characters.
                void SetAllowedChars (std::string s); ///< Used to define which characters are allowed to be typed. If '\n' is ommitted then it's not allowed either
    private:
        glictColor bgcolor;
                char passprotectchar;
                std::string allowedchr;
};
#endif

Now.. Here are my questions: 1) What can happen to my project if I leave SAFESESH "OFF"??? 2) What am I missing in the link error?