I have just installed Slackware 13.37 which uses kde 4.5.5

I have noticed that when the mouse hovers over the icon of a jpeg in dolphin the popup thumbnail does not come up anymore. This works for me in previous installations of slackware with earlier versions of kde 4. Jpeg is selected in the preview list.

Is this a feature of kde 4.5.5 or a problem with my installation? If it is a problem how do I go about tracking down the cause. I suspect that there is a problem with the nouveau driver. Could this be affecting the pop-up?

Do you have tooltips enabled for Dolphin?

It wasn't. Thanks, that has it sorted!

Is there anyway to get hovering to show folder contents or has that been discontinued?

Settings -> Configure Dolphin... -> General -> Previews -> check Directories.

That shows me some information about the directory but does not allow me to browse simply by hovering.

Ah, you mean the popup in Folder View (e.g. on your desktop)? You need to hover over an icon and click on the little up arrow (below the '+').

That was it - folder view. I don't see a little up arrow

Google is my friend. The arrow does not appear with the Elegance theme I am using.

I had the same problem when upgrading. Ended up uninstalling the theme I was using and installing it again, along with deleting the cache in the folder ~/.kde4/cache-*.