'Knight Rider's' Rebecca Holden and Record Producer Husband Joel Diamond's Car Destroyed by Oak Tree

"Knight Rider" star Rebecca Holden and her record producer husband, Joel Diamond, got a rude awakening in the dead of night ... an oak tree came crashing down onto their property, and cost 'em a car in the process.

Joel tells TMZ ... he and Rebecca were awoken late at night Friday by a loud noise literally tearing through their Calabasas home. It turned out to be part of a nearby 6-ton oak tree that had toppled over for some reason. We're told the tree burst through their bedroom window ... and also crushed three vehicles down below.

Unfortunately, one of those cars happened to be Joel's prized classic Jaguar -- the back end of which was absolutely demolished by the fallen timber. A total loss, no doubt. What sucks is Joel tells us he'd just gotten the whip back from an auto body shop 2 days prior.

Nobody was harmed, thankfully, but it sounds like a few of Joel's friends were pretty impressed with the freak phenomenon. Singer Tony Orlando -- known for his #1 hit, "Tie a Yellow Ribbon Round the Ole Oak Tree" -- made a crack ... saying out of all the trees he'd ribbon'd over the years, Joel and Rebecca's was by and far the most outstanding.