Instead of having a tranparent background like this:
...my GNOME Activities Overview is having a solid black background. How can I get the transparency?
I figured it out. It seems to be a bug of the proprietary fglrx
driver. Some people recommend turning off the Have file manager handle the desktop
in the GNOME Tweak Tool
, but it didn't work for me, so I changed to using the open source ATI driver instead. It's working fine now.