Its hard for me to pin point an exact fix, but here are some ideas. In general issues like this are due to the width on your elements. IE is very picky, so if the widths are even a pixel or 2 off it can cause this issue of moving it down to another line.
Have you created you page in such a way that there is a main wrapper, then each column is either floated or has a margin left/right offset? The issue you are experiences isn't likely due to powerstore 2 itself since the home page looks pretty customized.
-justin
