The problem I see is with the way you've written your tag. If you specify a value attribute
you should not specify a body and visa-versa. It's confusing because the value in the body is different that what is in the value attrubute. Change your tags to:
<html:radio property="gender" value="male" />Male
<html:radio property="gender" value="female" />Female
Then just set the ActionForm property
gender to "male" sometime prior to displaying the page, and the male button will show as selected.