[citation][nom]sissysue[/nom]Waiting to hear excuses from all the MS fan boys on this site.[/citation]
Wasn't their a bug about a year ago that would cause some SMS messages being sent from Android devices to be sent to the wrong (random) recipient? Yeah, that happened.
Anyways, this appears to be a bug in the WP Messaging hub and not in the SMS/MMS client itself. The freeze can be caused by a facebook message or post, Messenger chat message, SMS, or most other chat clients that support the Messaging hub. This would also explain why it only affects 7.5 phones. It probably has to do with the way that message interacts with one of those clients and the Hub cannot reconcile the error. I wouldn't be suprized if it was caused by the facebook client, but I won't pass judgement until I hear more about it.