I figured this out and found the info on some other web page, but will share it here in the event someone needs to know:

This was on my 2003 ES 300 but should apply to other models as well.

If the battery is disconnected for any extended period of time, the computer will "forget" the limits of the power seat, and therefore disables the memory function completely until the limits are re-trained.

To do this, do the following with IGNITION ON (don't have to start engine)

1. Move your driver seat all the way FORWARD until it stops
2. Move the driver seat all the way BACKWARD until it stops
3. Move the driver seat back all the way FORWARD until it stops
4. Move the driver seat back all the way BACKWARD until it stops

Note: I read about it "beeping" on some models (SC430?) but did NOT hear any beeps on my ES 300.

After performing these steps, the memory function began working as normal. It took a bit of fiddling to get it fully working. I was able to set a preset, and then it would not allow me to set another one, but I believe the computer was literally learning as I was doing it so you may have to be persistent and keep playing with it, move the seat a bit and try again, etc.... basically keep playing with it, and a couple minutes later I seem to have fully functioning memory seats once again.

Hope this information is helpful. It may be here somewhere already but here it is.

 

Thanks for the tip. Good username.