Media Encoder Problems

Just got going on a new Mac Pro with CS4 last week. (snow leopard)

I don't really understand about codecs, but I feel like I understand enough to know that this isn't working.

I was attempting to use Adobe Media Encoder (CS4) to turn a wav to an flv for my site. Wouldn't work. Can play the wav via iTunes, Quicktime, Flip4Mac, etc - so that codec is there (? yes).

I only convert two file types normally, wav and mpeg4, so I decided to try an mpeg4 and that didn't work either. I can import them into Flash and they play, but I can't get my media encoder to work.

Any help is greatly appreciated. Everyone's always very helpful here, so I thought I'd give it a shot. Wasting too much time when this should be working. Need an 'expert' opinion, or any opinion at all...

Thanks for your time.