I set up a test board from scratch, so I did not import my boards, I just typed in some of the categories and forums to play around. Down in the Caribbean and Bahamas Section, I set up the Bahamas board to have attachment capability. I set up an images directory under ubbthreads, but I can't view attachment in post.

http://www.tropictravelonline.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/1/an/0/page/1#Post1

Images will only show "in line" when attached when they are smaller than (or the same size as) the limit set by the admin in the control panel.

General -> Primary Tab -> Topic Display Options -> "Max Size for inline uploaded images"

but it tries to download and goes to an error page.

Ive set the max and viewable the same size.

Not keen on the download thing.

So anything uploaded is viewable

Look in that directory via ftp or console and see if the image actually exists in that directory. Check permissions on the directory, make sure it's read write. I'm not getting an error, but I do get an empty page. Check the properties on the image file if it does exist. Is it 0 byte?