Firefox windows not merging with Firefox icon in Windows 7 toolbar

I have Windows 7. I have a Firefox icon always in my toolbar. Normally, it looks like this: [http://imageshack.us/photo/my-images/820/normalpn.png/ Picture 1] Whenever I want to start FF, I click the icon, and the icon itself expands and opens the window. In the following picture, you can see that the icon turns into a window. [http://imageshack.us/photo/my-images/402/normalexpand.png/ Picture 2] However, after I installed FF 10.0, I have been getting this result when I click the icon: [http://imageshack.us/photo/my-images/703/incorrecta.png/ Picture 3] It is extremely annoying because the original FF icon is still there, which takes up precious space on my toolbar. Does anyone know of a solution for this problem?