Effects Won't Work on Bus/Sends

Hello all,

I've got a problem getting effects plug-ins to work on the buses in one of my songs.

Here's the deal:

I have 8 bus objects in the environment. Inside the arrange window, I have vocals on two Audio tracks. I've created two bus channels in the arrange window and to each added an FX plug-in, SilverVerb (Bus 3) on one and DJ EQ (Bus 2) on the other.

On each of the Audio tracks, I added a post fader send to each bus. Everything was working fine the first day when I saved the song and shut down Logic Pro.

The next day I started Logic and opened the song to continue where I left off and the effects buses would not work. No matter what level I set the sends on the audio tracks to, there are no FX added to the sound - it's just dry.

I do not have the Plug-ins bypassed (I checked more than once), the gain is all the way up in DJ EQ and the 'Wet' percentage is at 100% in SilverVerb. What could the problem be?

Thanks in advance for any help.