IPhone :: Siri Locks Up When Responding To Messaging?

both my father and I are experiencing complete iPhone lookups when using Siri to create or respond to messages that come in. It is not completely consistent, but most often, if we receive a text or iMessage and attempt to "reply" via Siri, the phone locks up on the send portion. Siri goes through the prompts of what would you like to say, then reads the message back and prompts to send. When we reply to "send", Siri then states "Alright, I'll send the message, but the mic indicator keeps circling and the entire iPhone 4S locks up where only a hard reboot will clear it. This can happen when on the lock screen or home screen. This situation also happens when you ask Siri to generate a message, but typically not until a couple of messages have gone back and forth leveraging Siri then the phone again locks up on the "send" portion in the same way. Simply odd and frustrating behavior. There are a few times it will go through ok, but most often it will lock the phone up. That said, the dictation feature never hangs.

Info:
iPhone 4S, iOS 5.0.1