I looked at my personal settings: The frontpage settings look like this:
remove
o Chatterbox down
o Other Users up down
...
Keyword nodelet add o
Here the o denotes a checkbox. To remove select the checkboxes in front of the existing nodelets, to add select the checkbox after add. (This is for Galeon, which uses the Gecko engine.)

I tested the page also with Opera 6.11, Linux, there it looks the same.

I hope this helps.