"Default font substituted for missing font" message popping up all the time! Help!

I've been running into a problem lately... I've created hundreds of layouts on my Mac using InDesign CS2. When I open up something I've done in the past, even if only a week ago, I get the following message:
"Arial (TT): Default font substituted for missing font."
I have the entire Arial suite installed, so when I go to "find font," I pick ArialMT.
I do not have one called Arial TT and am not sure why it is looking for it since I obviously hadn't used it in the layout.
Is there some way to get Arial TT changed to ArialMT across the board on all my InDesign docs? Having that error message pop up all day long when I am opening stuff is just getting to be so annoying. Just wondered if this rings a bell w/ any of you.

All of my indesign documents are always "missing Times TT", even though it is nowhere to be found in the document. To me its just another step to saving a pdf now. I just ignore it. But a fix would be appreciated.