Hotmail bouncing email

Is anyone else out there getting reports of hotmail randomly bouncing emails with just a message of "failed"? Over the last 2 weeks we've had a dozens of complaints of hosting customers spanning dozens of domains not receiving emails from hotmail users. Checking our logs shows the messages were never even attempted to be delivered and all forwarded in bounce messages literally just say "Delivery failed", yet we are still happily processing thousands of other emails from hotmail everyday. Now I'm wondering if this is restricted to us in someway or part of a larger problem.