Centered image with a link

My centered images with links are behaving differently in IE and Firefox (not sure what’s happening with other browsers)..

IE has the expected result of just the image being hotlinked — mouse changes icon when hovering over image.

In Firefox, the entire block the image is in is hotlinked — mouse changes icon when to left and right of image, not just within image constraints.

Can anyone assist with the solution to this? ?? Here is my css code for my image centering class:

img.center {
display:block;
margin:0 auto;
border:2px solid #88A;
-moz-border-radius:6px;
padding:4px;
background:#FFF;
}

Thanks!