I just did my first back up with TM and My Passport for Mac, when done adn went into the box ....options...to try and fidn how to delete trash. Then I went back to see if it was erady to do its next scheduled back up and it says there is an error. What do

I just did my initial back up to hard drive (My Passport for Mac 1TB) with TIme Machine on Snow Leopard. I had wanted to omit trash but couldn't find it. All went great and finished in an hour. Then said would restart at 6pm. I went into options about 20 minutes before (when it was done initially) to try and find how to delete trash from being backed up next time.. THis messed things up and now it doesn't recognize the disk and won't let me manually back up...says error. What do I do?

JD in AZ