Double IM alerts with iOS 5

[RogerSC]

Since upgrading to iOS 5 on my iPhone 4, I've been getting the normal first alert for an IM when my phone is locked. The bell rings and there is a notification window on the front of the phone. However, if I just leave it alone, about a minute (more or less) later, the bell rings again, same notification window on the front of the phone for the same IM.

I've power-cycled and rebooted the phone, set Notification -> Messages -> Repeat Alert to "Never", and this still happens.

Any idea what might be going on, or how to fix this? I really don't like it, once is enough for this *smile*.

Thanks for your help.