checkbox while tabbing

hi,

I am working on Adobe Livecycle Designer 11. there is one questionare section. while tabbing if i check the Yes option,

an alert box pops in. If I tab to the next option(NO checkbox) and click  it, then ideally the previously checked "YES"

checkbox shoulld get unchecked but it does not. In the No section there is one "WARNING" message box. until I don't click it, the "check" mark on YES checkbox does not get unchecked.

Please suggest me the solution.