I googled Acura transmission problems & found this on Wikipedia (you've probably already seen this):
2000
In the second year of production, the Acura TL was given slightly more features, including a 5-speed automatic transmission, with SportShift. The added gear allowed for slightly better fuel economy and acceleration when compared to the previous 4-speed automatic transmission with SportShift. With the this model if the driver forgets the 1-2 shift the computer would take over when in sport mode and do the 1-2 up and down shifts unlike the 4-speed 1999 model. In many vehicles, the 5-speed automatic transmission failed: as the third clutch pack wore, particles blocked off oil passages and prevented the transmission from shifting or holding gears normally. The transmission would slip, fail to shift, or suddenly downshift and make the car come to a screeching halt from expressway speeds. This problem was highlighted in the Los Angeles Times in September 2002. Consumer Reports took note and gave the TL and CL the black spot, the worst rating for transmission reliability. In response to the recurring problem, the manufacturer extended the warranty covering the transmission to 7 yrs or 100,000 miles (160,000 km) on U.S.A. models. A class-action lawsuit was settled to extend the transmission warranty for U.S.A. owners or entities but not Canadian owners to 7.75 years for all 99 to 02 and some 03 by VIN. For details see: [1] Transmissions replaced prior to March 2005 usually fail again. Transmissions replaced March 2005 and later include a redesigned third gear clutch pack reported to fix the problem.
Looks like the problem was limited to 1999 to 2002 (some 2003) models. I had a 1999 TL that didn't have this issue. I do remember that I was given the warranty extension.