2004 H2 Tranny Problem

[isellpower]

95K miles and never any problems until now. Drove to a party about 20 miles away then back home with no problems what so ever. No kidding, literally as I turn into my driveway it starts to slip and goes nowhere. I left it there and took my kids inside. Went back out, put it in reverse to see how that would go and it backed up just fine. Low and behold when I put it back in drive it drove just fine. I went around the block and it drove just like before. Any ideas?