I got this problem too, but it wasn't the xoops's fault, it was mine. The network setting were a mess (company retard offered to help) and had to re-make the whole network.
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bedroom furniture

THANK YOU TREMENDOUSLY!!! I have searched all over the XOOPS FAQ's and Google and could not find an answer to why I could not see any images from Remote computers. After I specified the IP address, instead of localhost, everything worked well. I also had to specify the IP address for web banners in the Control Panel for them to show up. All-in-all, this took me about 5 minutes. Take care and keep up the good work..!

//Nikishna

Some cautionary tales.

1) If you build XOOPS sites on a laptop PC connected to your network, using the router's dhcp IP address in mainfile enables you to view the site from elsewhere on the LAN. However.. if you dis-connect the laptop and take it to a meeting to show someone the site, you will need to re-set mainfile to use 'localhost'. I forgot this myself recently and 10 mins before the presentation got a 'Page not Found' error in the browser!

2) The XOOPS image manager and some WYSIWYG editors insist on using absolute URLs for images. If you upload a site to a live server, any hard-coded image references will remain as per your network PC. When you view the site, the images will appear... but they are being loaded from your computer, NOT the site. You can see them, but nobody else will be able to until you change the links.