2001 Acura CL Rapid transmission fluid leak

We were driving on the highway about 75 mph for over an hour when suddenly the dash engine warning lights came on and then we saw white smoke coming from the engine. We pulled over immediately and found a severe leak (seeming to come from both sides underneath the car) that at first we thought was oil but later found it was transmission fluid. The car did start again upon trying but we immediately turned it off and got towed to the nearest dealer which happened to be Honda. Honda hooked it up to their diagnostics and the code indicated "incorrect gear while in drive". There had been no warning signs, nothing unusual in the way the car was driving, no transmission slippage, etc. I realize Cl's have a history of transmission problems and my transmission was replaced back about 50K miles or so ago with no problems since then. We get regular oil and air filter changes, new brakes, new tires but no other major work. I'm hoping I don't need a new transmission; perhaps this is a modulator valve issue-? Any thoughts and approximate prices for a fix would be most welcome. Thanks.