That's another good lead to solving the mystery!
I can tell you why the next day it was OK: you probably ran an update or installed a package. You have to run SuSEconfig as root to apply those icon changes.

With your tip, I got the Send/Receive button, but there's a whole whack of them still missing.

However, I did not have a 'tango' folder in my /usr/share/icons. I assume you installed the icon-theme-tango. Did you do that on purpose, or was installed by something else?