Yes, it's to do with your host, or at least the default URL format you are copying from that host. If the URL doesn't end in something like JPGor another normal, supported image extension, the BB code doesn't seem to interpret it as an image when wrapped in the img tag.
You've been using URLs like
<!-- m --><a class="postlink" href="
gallery.me.com/seanwallace/100013/230920...g?ver=12537431520001">
gallery.me.com/seanwallace/10001 ... 7431520001
If you wrap that in the IMG tag it just won't work.
If you remove the ?ver=blahblahblah at the end, you should be able to do this:
[img:3168pcuu]http://gallery.me.com/seanwallace/100013/23092009%28005%29/web.jpg[/img:3168pcuu]
[b:3168pcuu]However, note that that is a pretty big image, and is not friendly to low-bandwidth or mobile users (like me <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt="

" title="Smile" /><!-- s:) -->). [/b:3168pcuu]
I like to use photobucket and use the thumbnail URL to show the image in a post, and then wrap that in a URL tag to allow users to click on it and see a larger (non thumbnail) image. A bit like this (check the properties the image and compare to the Image URL, there's a "th_" at the beginning of the image name to indicate thumbnail):
[img:3168pcuu]http://i479.photobucket.com/albums/rr156/barrymasterson/th_PumpkinAle-TheIngredients2.jpg[/img:3168pcuu][/url:3168pcuu]