I did these tests on Linux, with doxygen compiled from svn (684)
file test.c

/*! my spectacular enum */
enum E {
    one, //!< I
    two, //!< II
};

/*! my spectacular struct */
struct S {
    int  *i; //!< integer doc
    enum E  e; //!< enum doc
    enum E  *ep; //!< enum pointer doc
};

void main()
{
}


Doxyfile modifications 
OPTIMIZE_OUTPUT_FOR_C  = YES
EXTRACT_ALL            = YES
INPUT                  = test.c


In the generated S Struct Reference page the 'ep' field is absent.

If there's anything I can do to help resolve this issue, please let me know.

Thanks for the wonderful tool anyway.

Bart