Recently, I'm having a problem with items not appearing on my desktop (at least not right away) after just being saved there, forcing me to either find them in a Konqueror window (they do show up there) or do some other unusual thing to make the desktop notice them. They used to, and as far as I know, they always should.

For instance, I just took two screenshots with Ksnapshot, and told it to save them on my desktop. It saved them, but they didn't show up on the desktop. When I noticed that, I opened the desktop folder in Konqueror, and mainly to see what would happen, tried to drag the screenshot files from the Konqueror window onto the desktop (copying the files onto themselves). That made the desktop notice the files--they appeared. But of course I shouldn't have had to do it. What could be wrong?

I assume you are using the KDE desktop environment. I think that is a new "feature" in KDE since 4.1. KDE removed desktop icon support in favor of the use of applets or widgets or some such thing, in the name of a clutter-free desktop experience. I prefer that when I send something to the desktop that it actually shows up there, which is why I prefer GNOME but I think you can change this behavior in KDE. But, I digress, you can read more about this feature here. I hope this helps, maybe one of the KDE pros can help you get your icons back.