Why do I have an "iMessage" and an "SMS" thread for my contact? I recently updated to iOS5, One of my friends messaged me through iMessage, the sender name was his @gmail.com address.

The message appeared in a seperated thread to the existing SMS messages I had with him previously.

I added his mail address to the contact I already had with him, however I cannot get the iMessage thread to merge with the SMS thread.

I have tried deleting the iMessage thread with no result.

If I open the SMS thread, it will only send SMS.
If I open the iMessage thread, it will only send iMessages.

Is there a solution to let me merge these two conversations?

Phone is an iPhone 4G 16GB.
iMessage threading is a total mess. I have an iPhone 4 and an iPad 2, both with iOS5. So does my brother. Not including regular SMS messages sent/received with iOS4, I now have three different threads of messages from him on my iPhone, seemingly depending on which device the message was sent/received on. I have two on the iPad, but these don't correspond exactly to any two from the iPhone.

I understand that iMessage (like FaceTime) can only address contacts by email address on a WiFi-only iPad, and can address by both email and phone number from an iPhone, but these all resolve to the same Apple ID on the server, and to the same contact on the device. Surely it should be possible to merge these conversations, either on the server (by Apple ID) or on the device (by contact).

Perhaps a fix will appear in a future iOS update but for now this rather takes the edge off an otherwise cool new feature.