Cars - Strange electrical problem with my '00 300M

So this morning I start my 300m for my 1.2 km commute to work. Car
starts and idles just fine. I put it in reverse and back out of garage.

I notice that the (ABS) light is on, and so is "Trac Off" light.

Hmmm. Ok.

I continue my drive to work - car seems to run just fine. Those lights
stay on.

I get to my office, park, turn car off. The factory in-dash CD player
blinks it's lights several times.

Hmmm. I remember it did that back a couple years ago when I still had
the factory-original battery in the car, and the battery capacity was
pretty much worn out, and the CD player would blink it's lights
occassionally after starting the engine.

So I just leave the car as-is and go on with my day. A few hours later
I decide to see if there are any codes to display. I do the
key-on/key-off thing 3 times, and I get only 1 code: P-1684.

Basically, a code that just says that the battery has been disconnected
within the last 50 starts.

????

So a few hours later when I leave my office, I start the car, it starts
fine, no codes, no warning lights, and I drive home, no issues, turn off
the engine, the CD player does nothing.

Any ideas???