Theme widget size problem

I have installed WordPress 2.5 and it is running fine, but when I go to the administration panel and select any theme which has widget. When I try to customize it, widget size become big and all its useful buttons like remove and modify hide inside another layer. Please see the pictures..

This is picture of widget when collapse(text widget)
http://erealmedia.com/WP25/widget1.JPG

This is same widget when it is expanded for editing. Most of its part is hidden behind another layer. (Like remove and modify buttons)

http://erealmedia.com/WP25/widget2.JPG

This full widget picture, but I have draged with holding mouse. When i release mouse to modify, then widget moves back to normal position as shown in picture 2.

http://erealmedia.com/WP25/widget3.JPG

PLease help me to resize- or solve this widget problem so that full widget can be seen and modified easily.