Can you PM or post here, your forum URL?
When you added the new user profile field, did you add the option of Male & Female?
With regards to the ":" just remove it from the code (In bold-RED), below:
Code:
<!-- Wy Gender in postbit Start -->
<vb:if condition="$post['fieldX']"> <dt>Gender:</dt> <dd><img src="http://WWW.YOUR FORUM
ADDRESS.COM/images/misc/{vb:raw post.fieldX}.gif" alt="" /></dd></vb:if>
<!-- Wy Gender in postbit End -->