I have the ABS/VDC issie too and after reading a few posts wonder if most people are having the same simple issue.
Do you normally only get it the wet?
Does it normally occur with brake pedal application?
Did you have the problem and by replacing the battery it went away?
I am wondering if the main issue is power fluctuations. When its raining you will have the wipers and perhaps lights on putting more of a load on the electrics, then when you press the brake pedal the load is incr further by the brake lights and "Beep" VDC/ABS warning. I personally notice that when i have the lights on the indicators when they are first selected make the lights dim for just a sec.
The first thing I am going to check is the battery and charging circuit, then go onto wheel/steering sensors etc.