03 Santa Fe locks up
 

My '03 Santa Fe 2WD V6 2.7 has recently started "locking up"...It cranks great but when I put it in Reverse or Drive, it won't go...It feels as if something is "locked"...I feel it going in gear but nothing happens...Even when I put it in Neutral it WILL NOT roll with two grown men pushing it!!!... If I slap it back and forth between Reverse and Drive and eventually it goes....Can anyone help me?...This has happened twice in 1 week...Also, I just had a transmission flush at the dealership yesterday and they said everything looked good with the tranny...Thanks!