"Buss" and "Plug in" words grayed out...

[amba]

Hello and greetings from Packerland...yes...the Vikes beat us today...

Quick question that I can't find anything on in the FAQ and Search...

First...

# Computer model and processor speed---iMac 2.4 Ghz (Pre duel core intel)
# OS version---OSX
# Pro Tools version---7.0
# Amount of RAM installed---4 gig
# Any attached peripherals (hard drives, video devices, other firewire or USB devices that may be attached, etc)---one firewire 80 gig Glyph
two internal...

I created a new track, Aux/Mono...and then in the mix window went to the Input, Mic/Line 1-4 Analogue 5-6...and wanted to buss an inserted mono D-verb...but the Buss and Plug in buttons/tabs/whatever are grayed out...why?

Thank you very much,
amba