Doesn't show here but it will show the thumbnail version next to my name underneath this question. How come?
Did you recently change it? It may be that it's "cached" on Gravatar's servers (since we're both in the UK, could be cached only here for some reason). For example the URL is basically the same:
https://www.gravatar.com/avatar/f82e8af257aadb42418cf24d5e46e5b3?s=60 shows the correct image, smaller https://www.gravatar.com/avatar/f82e8af257aadb42418cf24d5e46e5b3?s=200 shows the G logo, large https://www.gravatar.com/avatar/f82e8af257aadb42418cf24d5e46e5b3?s=201 shows the correct image, one pixel larger
So... not sure what the problem is.