I have read related questions here, but my problem in 11.10 is:
I have no "startup apps" item in "system setting" at all. How can I get it back?
Read it here ....
hope it helps
I was searching the system tray issue and came across the parting laments regarding Unity.
All you have to do is open your terminal and type
sudo apt-get install gnome-or-search gnome-fallback for gnome shell options. The only thing I missed was Users and Groups, it seems Gnome tools were not included, but another search found that as a solved issue (so the package is available).