bmearns

also make sure you clear your cache and refresh after doing this … wp caches a lot of stuff

To fix this you just need to add the lines applying to .img from style.css from the default wp theme to the style.css in your theme. Here are the lines I had from wp 2.5 default theme:

img.centered {
display: block;
margin-left: auto;
margin-right: auto;
}

img.alignright {
padding: 4px;
margin: 0 0 2px 7px;
display: inline;
}

img.alignleft {
padding: 4px;
margin: 0 7px 2px 0;
display: inline;
}

.alignright {
float: right;
}

.alignleft {
float: left
}