Ian,

Take a look at http://www.peachparts.com/shopforum/showthread.php?t=254705

I saw excatly the same thing comming, the ASR and ABS light turning on now and then, until one day it was constantly on, besides a lot of other odd things to follow like no stop light, the top not working now and then, the temp indicator dropping to zero etc...

It turned out I was a couple of bad wires - loose connections - turing into a serious problem over time. Look for bad connections in general, and ground connections specificly.

Rud