Problem with visibility true and false with iframe-Flex4

[bindum]

Hi
I am having a xml that contains html paths. i parse the xml and send all the html paths to display in an iframe. it renders properly.
now i have links on right side, clicking on the link will get another xml that contains its own html paths. i removed all the previous elements , and load the 2nd xml . it loads but when i made the visibility false and then true on a button click the iframe from previous link 1st xml will become visible.
How to remove all the existing iframes and load new xml ?

Please help.

Thanks .