[IMG] problems
 

I'm having some major problems with the [img*] tag on my board...

I would use the following code as an example:

[IMG]attachment.php?postid=3348[/IMG]

but as you can see, the IMG tag shows, and does not convert it to an image box... even though it is enabled. I think it is because of the ? - is there any way to get past this?

Enable Dynamic URLs for [img] code on the vBulletin Options page in the ACP.

Still doesn't work :(

Any ideas how I can check, or bypass it?

I assume you are using the full URL and not just attachment.php?postid=X as it won't work unless you use the full URL to attachment.php.