The same thing happened to me about 6 months after I bought my used 300e, I left it for approximately a year. Then the light came on more frequently until one day I was left stranded, with the car losing all electrical and then power while driving. I ended up replacing the OVP, and then the Voltage regulator. I think it had to do more so with the voltage regulator, as comparing the new vs. the old, the two bushings were so worn, it's a wonder I had any charge at all.

I doubt its the ABS at all.