1999 GMC Savana power door locks spasm

The power door locks continually try to lock and unlock while we are driving without success, they just spasm. When the drivers side lock and unlock switch is pushed it doesn't open or close any of the other doors. When the passenger side button is pressed it will only occassionally open the drivers side but with resistance. We have unhooked our security system thinking this may be causing the problem but it is still happening. We took it to a mechanic and he has told us that something is getting two positive signals and he has gone over the wiring scematics without any success at finding the problem. He tried all of the locks individually and they work fine. Furthermore to add to the frustration when the doors spasm it eventually blows the cd player fuse in the van which runs on a different fuse. Its driving us crazy. Any help would be appreciated. Thanks.