FlexiGrid overlapping bgiframe in ie6

Hi
For layout issue in IE6, I have used bgiframe for a pop up.But that bgiframe comes behind jquery flexigrid component which is not suppose to do so.I want that bgiframe to come above that flexigrid component.Any reason why it is blocking bgiframe?....can anyone give me a solution?....

Thanks in advance.

Regards,
Imran