@paxsu and others interested in this: I found the same problem and was surprised, as hovering over links (to see the URL in the status bar at the bottom) had indeed worked in Opera for me, just moments before it stopped working. That's when I came searching for any solution and found this post, among others.

Here's a workaround that's worked for me: all I had to do was click on some text in the page (not a link, I mean) and then hit the tab key. Suddenly now hovering Did show the URL in the status bar, and of course tabbing to a link Also shows the URL.

While I can't figure out what makes it suddenly Stop working (sure, could be some extension, or could just be a bug), at least discovering this has allowed me to immediately see the URLs again, which is indeed important for safety sake. Hope that helps others.