What did you do?
Here's the steps I took:
go to your profile
click "change my photo" under your current profile picture
Next to where it says "profile photo", there should be a tiny thumbnail of your current photo and a square for you to click. Don't forget to allow scripts, otherwise it won't show up. If you don't know what scripts are, you probably don't have to worry about it.
Select "Upload an image from your computer"
browse for a photo
and don't forget to save your profile.