Comment # 7 on bug 953954 from Wolfgang Bauer

(In reply to Jaroslav Kamen�k from comment #6)
> I don't know what have happened in last days, but I do not see even Opera
> icon now, it was visible before. So I have 3 blank space in ty now, do not
> see new mesages in pidgin and so, little anoying;).

I ask you again: does the workaround help?

Enter the "System Tray Settings" (via right-clicking on the system tray), turn
off the "Miscellaneous" category e.g., press on "Apply", then turn it on again
and press on "Apply".
All your icons should appear then.