Missing expander arrows in some tree views

There seem to be some missing expander arrows in certain tree views. The two primary cases I have noticed thus far, are in Seahorse and in Evolution.

In Seahorse, there are now expander arrows next to the keyring "folders" in the Passwords tab. Changing the theme to Adwaita while Seahorse is running, will make them appear. Changing back to Ambiance also lets them stay visible. However, upon restarting the program, they are gone again.

In Evolution, when choosing Folder->Subscriptions from the menu, the resulting dialog has no expander arrows, and all of the entries seem to be fully aligned to the left, rather than having children appear properly as children, even though the "Expand All" and "Collapse All" buttons will make various folders appear or disappear respectfully. Changing the theme has no effect on expander arrows appearing here, nor does it change the alignment. This may actually be an Evolution bug, but it is hard to say for certain at this point.

I am however, pretty certain that the Seahorse issue is a GTK+ bug, given the behavior, and that it happens with the Default GTK+ theme.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: libgtk-3-0 3.4.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-20.32-generic-pae 3.2.12
Uname: Linux 3.2.0-20-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 1.95-0ubuntu1
Architecture: i386
Date: Fri Mar 30 09:19:22 2012
SourcePackage: gtk+3.0
UpgradeStatus: Upgraded to precise on 2012-01-12 (77 days ago)
modified.conffile..etc.gtk.3.0.im.multipress.conf: [deleted]