Two legs I have, and this will confound: only at rest do they touch the ground!
What am I?
Hmm. That's a good one. :)
Wheelbarrow
Touch the ground simultaneously?
Grrr...
http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2004-11,GGLD:en&q=Two+legs+I+have%2C+and+this+will+confound%3A+only+at+rest+do+they+touch+the+ground%21
Re-phrase your riddles. :)
Rephrasing it made it sound less catchy.
I already knew that one btw, I saw it a few days ago.