I've been doing some serious yard cleanup and when I was finishing up the last of the bucking on an oak with my Husqvarna 455 Rancher, I momentarily sank the bar tip into the dirt when the log shifted. The chain immediately stopped dead in the cut, and now it will not rotate at all by hand, even with the chain brake disengaged and the bar nuts loose. The engine still fires up fine and sounds normal, but the chain just won't budge, so I can't even get it apart to clean things out. I’m concerned I might have damaged the clutch drum, the clutch itself, or maybe jammed the sprocket tip with a huge clump of dirt and debris. Has anyone run into this exact total lock-up after a sudden impact? Is this something I could fix?