Adblock seems to be incompatible with latest colorzilla.
I'm Using Fx1.5b1 latest AdBlock 0.5.9.20050917 and colorzilla 0.8.3
With both addons enabled adblock refuses to show up in the statusbar - neither icon nor text will display. When I disable colorzilla the status bar display works.
I was able to reproduce this with just these two addons enabled and default theme.
Anyway both addons are fully functional, so its merely a cosmetic issue.
(Note that the colorpicker icon of colorzilla is aligned to left by default. There was something with icons on the left and adblock not showing?)
colorzilla can be found here: http://www.iosart.com/firefox/colorzilla/