When you are creating a new topic or replying to a topic (or sending a PM or creating a dictionary definition) you will see two green bars below the message area labeled "Upload" and "Attach." When you click the Upload bar it will expand out and allow you to select and upload a file to the message you are about to post.

Sometimes that bar will not expand fully and it will look like this:



The problem that you see above was caused by CA's ad/pop-up blocker being set to medium. By setting this to off it resolved the problem.



Some ad/pop-up blockers can be set on a site-by-site basis. If you find that your ad/pop-up blocker is also blocking features on this site and forum then you might be able to disable it just for this site so that you can still use the site's features.