Hi Chevelle,
I had the same problem about a month ago. The dealer ended up replacing the 4WD module. In the meantime to make it driveable, once you shift it into 2WD remove fuse 15. I think its 15, check the back of the cover to the fuse box. This will allow you to drive without the 4WD system powered up. It shouldn't switch automatically anymore, but you also lose your fuel gauge indication so make sure you know how far you can drive.