Look at the tensioner and idler pullies. If there is no looseness in the bearings, look at how the tensioner pulley operates. Some are spring-loaded. When the nut is loosened, the spring is supposed to set the tension, then you tighten the nut. It is possible for the unit to stick so the spring doesn't pull it tight enough.
Some engines use a real heavy spring inside a cylinder. Those must be unbolted from the engine and compressed in a vise to get them to retract. Then you lock it with a pin, such as a cotter pin and reinstall it. The pin is removed after the timing marks are set and all slack is on the side by the tensioner. There's no point in gong through all that since you obviously know the procedure already, but if you can retract that plunger by hand, it's not strong enough.
I'm leaning more toward a pulley alignment issue since a tensioner problem is more likely to allow the belt to jump a tooth or two, not shred. Any chance the plate is missing or the rib is broken off on the end of the crankshaft sprocket? You might try running it with the covers removed so you can watch the belt. I never fully trust my work until I see that belt working properly.
Also, if you didn't, you should rotate the engine by hand in the normal direction two crankshaft revolutions, then recheck the tension. If the belt is a little loose, it could vibrate and flop around and bang into stuff. This would be more suspect if the original belt just broke from age. If the original belt and the new one both shredded the same way, suspect a pulley problem over an installation problem.
Sunday, March 21st, 2010 AT 12:58 AM