Re: i Message
Typically a red exclamation point or a reversion to normal text messaging (green bubble) is a sign of network difficulty...either you're in an area where the network is not supportive of the iMessage feature, or the iMessage server is having a problem itself (this happens occasionally, but is usually reflected on forums with multiple reports of it...and I can say that today, I have had zero issues with iMessage).
You can try resetting your network settings to see if this fixes any issues with cellular connections (this will also reset your WiFi network settings as well, so be aware of that). If the issue continues in areas where you know you have solid connectivity...it may be time to restore your iPhone via iTunes (make sure you have a decent back up before doing this).
If all else fails, take it to Apple and let them replace it (or if it's out of warranty, at least look at it to see if there's any obvious answer for you to consider repair for).