Double popup in IE6

When I click the folder/file details or the fileupload, IE6 opens 2 new windows intead of 1. 

The first is a blank page with the right dimensions(height and width). 
After that a lager window  opens with right content, but wrong dimensions (heigth and width).

In Firefox no problem with the popups

Anybody the same problem, and ofcourse the solution, if you please?????

Thanks