Like what they have said and posted on the previous links your Avatar will take time to change in the upper right section but every time a member sees your post what they are seeing is the new one you have uploaded, it just takes time for you to personally see it. Try logging out of your account and visit a link where you have posted, you will see that you avatar has been successfully changed. Don't worry about this too much as this is just a delay, even when I was a full member back then I got worried just like you so I just searched some threads first to know if I have a similar problem that is when I knew that this is a common occurrence.
Got it, thanks Theb.