TechBuji.com

The fix is posted in http://wordpress.org/support/topic/170320?replies=12#post-741557.

I am just copying it for easy reference.

Look in thickbox/thickbox.css

Around line 50, change all the below

#TB_window {
position: fixed;
background: #ffffff;
z-index: 102;
color:#000000;
display:none;
border: 4px solid #525252;
text-align:left;
top:50%;
left:50%;
}

To

#TB_window { /* my IE7 Hack*/
position: fixed;
background: #ffffff;
z-index: 102;
color:#000000;
display:none;
border: 4px solid #525252;
text-align:left;
bottom:10%;
left:50%;
}