Originally Posted by 70GT6

Very strange..I just had the same problem.
Last night my idler pully bearing seized. Upon a quick inspection I did mot notice any major damage. Looks like the bearing seized and the bolt holding the idler backed out, idler dropped on the pan and threw the belt.
Left a message for Jerry earlier today, waiting to hear back, maybe on here is better.

*Edit - mine was not rusty looking at all - just completely locked up.
Also when an checked the factory idler - same basic part number but different manufacturer, factory was a Timken.