Took the bike to my dealer...they advised that once my particular ABS sensed something was wrong (either with dirt on the sensor, or me not removing the front sensor during the knobby tire change) the bike would not reset the ABS and they had to reset it via their computer.
It seems to work fine now.
Is there any further wisdom on this issue? I had the same problem 09 800GS.
fitted Heidenau K60s. ABS light comes on after 10 or so miles. Doubt it is the tires, since problem showed up 500 miles after tire change.
Motowalt - did your problem stay solved after the dealer reset your ABS?