I am having the same issue on my GS300. Sometimes the fog lights are on, sometimes they are off (when in the on position), and often times when I they are on or off, using the turn signal turns them off or on (if they were on or off) ;)
I also have a "clicking" noice that comes from the turn signal switch occasionally when it's at the top or bottom of it's middle (non-turning) position. I was thinking these are related, but have yet to do find any solution.
On a related, or unrelated note, I also here that same clicking noise (coming from the dash) when my rear wheels loose traction, and the VSC kicks in.
Anyone else experience these issues?