Doxygen version 1.7.1.

The example C code below reproduces the issue:

//START
/*! 
    \addtogroup MyGroup
    \{
*/
typedef float MyType[4];            //!< A fixed-size float array

/*!
    \brief A function.
*/
void foo(
    MyType          out,            //!< output
    const MyType    a,              //!< input param 1
    const float     b = 0.0f        //!< input param 2
    );

/*!
    \brief A function overload.
*/
void foo(
    MyType          out,            //!< output
    const MyType    c,              //!< input param 1
    const MyType    d               //!< input param 2
    );

/*!
    \brief Another function.
*/
void bar(
    float*          out,            //!< output
    const float*    a,              //!< input param 1
    const float     b = 0.0f        //!< input param 2
    );

/*!
    \brief Another function overload.
*/
void bar(
    float*          out,            //!< output
    const float*    c,              //!< input param 1
    const float*    d               //!< input param 2
    );

/*! 
    \} Close Doxygen Group 'MyGroup', do not remove
*/
//END


The expected behaviour:
There should be two entries for foo and two for bar in the generated docs - one for each of the overloads.

Actual behaviour:
There are two entries for bar, but only one for foo.
The one entry for foo contains the brief of both overloads, but not all other details.
Here's a textual representation of the (incorrect) doxygen html output for foo...

//START
void foo ( MyType        out,
           const MyType  a,
           const float 	 b = 0.0f
         )

  A function.

  A function overload.

  Parameters:
        out  output
        a    input param 1
        b    input param 2
//END


And the same (correct) for bar...

//START
void bar ( float *       out,
           const float * a,
           const float   b = 0.0f
         )

  Another function.

  Parameters:
        out  output
        a    input param 1
        b    input param 2

void bar ( float *       out,
           const float * c,
           const float * d
         )

  Another function overload.

  Parameters:
        out  output
        c    input param 1
        d    input param 2
//END