on two different machines I sometimes notice that the graphical user interface abruptly hangs when a notification is to be displayed. The system usually returns back to life after a minute or so, but quickly switching to the VT and executing killall notification-daemon brings back to life the system immediately. From what I noticed there are some applications which cause the symptom to happen relatively often, while others never, namely Firefox and banshee seem to be problematic while for instance emesene, or even manually sending notifications via /usr/bin/notify-send always seems to work fine.
Is anyone else experiencing this issue or have any valuable information? Thanks!