98 Explorer only goes in reverse

[wolverine04]

Hello,

My friend owns a 98 Explorer. Last night as he was at a stop sign, the truck refused to go forward for a couple minutes. He kept pushing on the accelerator and eventually it went. Ok, fine. THEN a few minutes later as he was pulling into a parking lot just down the street the truck came to a hard stop (making a very loud noise while doing so) and once again wouldn't go forward but a couple inches no matter how hard or how many times the accelerator was being pushed. The weird thing is that the car will go in reverse just fine...so we backed it all the way up into another parking lot where it is still sitting this morning. I'm thinking something is wrong with the gears but I am no expert. Any ideas? I've never heard of this problem before.