Can't see "#include <vector>"???

Below is the top most of my header file, am I using "#include <vector>' or vecotr<> x incorrectly? I get an error:

"error C2143: syntax error : missing ';' before '<'" at the line "vector<el_t> el;"
which leads me to think that my compiler is not recognizing vector even with the vector include line above. Visual Studio 2008

Code:

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#include <vector>
typedef int el_t;    // the el_t type is int for now
                    // el_t is unknown to the client
class stack
  {

  private: // to be hidden from the client
               
          vector<el_t> el;
        //el_t    el[MAX];      // el is  an array of el_t's --int's (original line)
        int      top;          // top is index to the top of stack
          void stackError(char*);    // utility function for error handling

  public: // prototypes to be used by the client
................

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Code:

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std::vector<el_t> el;

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Kurt