Dont bother
I have been trying for years and I still can not do it
If I could this week my avitar would be a photo of a downs syndrome girl with the caption 'Heres the thing I have a really awesome life and there is no pre natal test for that'
Facebook members will soon see it as my profile picture
I'm not the most technically minded user but I found the process went smoothly, and I've successfully made temporary changes (eg to add a Christmas hat). At what point did it fail for you Ric.ror? I think the most common problem is failing to use the same email address on gravatar as is used on AB