Please Help - ABS Problem

I have a 2000 Suburban, and I am having false activation on my antilock brakes (No ABS Light comes on). "ABS Recall" was done last November, and I just developed this problem this July. I brought the car to the dealer, and they orginally said it was the "BCM Ground". When I picked it up from the shop on Friday, the ABS activated, worse than before, even in reverse. Brought it it right back in. They have been troubleshooting this problem half the day on Saturday and all day on Monday, and they still can't seem to locate the problem. I asked them if they performed the "Recall" cleaning again, and they said that they did and the ABS still activated. :banghead:
Can anyone give any comments or advice?

Thanks in advance,
John