First Comment do not show Avatar

I am using gravatar enabled comments on my blog but the first comment on a post do not show any image. The subsequent comments are fine and do show images or a default gravatar image. you can check a sample at the link below. Please do help me.

http://pashtolyrics.com/2012/07/sta-pa-toro-sanro-ke-lyircs-humayun-khan/#comment-19