243 votes. 61 duplicated bugs (as of this post). 21 backtraces submitted as attachments. 5 months of troubleshooting. 1 detailed Valgrind log. And now, Aaron Seigo has figured out and fixed Bug 258706, a crash in Plasma related to the system tray (often but not always with Amarok).
The problem? In basic terms, a QIcon was able to outlive the custom KIconLoader that was used to actually load the QIcon’s pixmap. It’s hard to properly share the underlying KIconLoader without breaking compatibility, but it’s not hard to figure out when the KIconLoader is deleted by using QWeakPointer. So, Aaron’s fix uses QWeakPointer to always have an up-to-date status of the KIconLoader used, and gives a fallback pixmap if the KIconLoader was deleted before the QIcon loaded the pixmap it needed.
If you’ve been hitting this bug, the fix will be in KDE Platform 4.6.4, although maybe your packagers will re-spin 4.6.3 packages to include this fix (hint hint ;)