Doc comments that contribute to the Serialized Form page do not get {@link} tags expanded in the expected way. See the Serialized Form page for javax.management.NumericValueExp for an example. {@link Number} shows up as "{@link Number}" in the output for a @serialField tag like this:
    /**
     * @serialField val Number The {@link Number} representing the numeric value
     */

The output can be seen here:
http://download.java.net/jdk6/doc/api/serialized-form.html#javax.management.NumericValueExp

It is conceivable that this problem comes from the fact that the class in question is not a public class. It is included via @serial include.
Bug 6662618 shows that the problem is not limited to non-public classes.