tray icons disappear

[shva]

I am using Ubuntu 9.04 for some while. Now it seems to have some problems with the tray icons: they just disappear overnight. For example, there is always a wicd icon every time I log in, but now it disappears (although network is still working). And there is always a tray icon for pidgin and every time I click the close button it minimizes into the tray icon. Now the icon is gone, and pidgin gets closed when I click the close button.

How can I restore my previous setting? Maybe I mistakenly deleted some package when I uninstalled some software... Thanks.

[shva]

Problem solved. It turns out to be quite simple. I somehow mistakenly deleted the notification area in the task bar. And when I add it back, everything looks like in an original way.