Looking in your page source, I see this as the image tag for a 'working' avatar:
HTML Code:
<img src="image.php?u=109&dateline=1228331423&type=thumb" class="alt2 avatar" width="60" height="45" border="0" alt="metalfreak85" />
And this is the image tag for the 'non-working' avatar:
HTML Code:
<img src="http://gamecolonial.com/gchome/forums/wi/misc/unknown.gif" class="alt2 avatar" border="0" alt="seal user" />
Looks to me like you need to set the width of the non-working avatar at 60 so it fits the space allowcated.