Maybe the bobbin case isn't in correctly. I took mine out and the needle plate off to clean the lint out and when I put it back together, I couldn't get it to stitch either. Everything has to line up perfectly in order for it to work. I highly recommend this book...it's got pics and was the only reason I was able to get mine back together again.
http://www.amazon.com/Featherweight-...ref=pd_sim_b_6