[jQuery] BlockUI problem with iframe in IE7

I have got iframe in the page and when I call blockui, the content
gets disappear in the iframe. This problem is only in IE7 not in IE6
and IE8.
I am currently using
* jQuery blockUI plugin
* Version 2.18 (16-APR-2009)
need to refresh with no cache for remedy and no problem if I do not
call blockui
regards,