How to get Sidebar Members photo’s looking round, not square?

Hello,

I’d like to set up the sidebar for all posts, as shown on the following website: http://www.datingyo.com/blog/

So, I added Members widget to sidebar but I got the following results. How can I fix this?

This also happens on other posts and pages (e.g. I created a Dashboard page and added Members but have the same square results). Strange thing is – the round works on Members Directory page, Homepage, etc.

Thank you.

Julien