Hi! I would recommend for all of you, who use firmware 12 and have unstable phone, that first format the phone * and # same time while turning on phone, and then format MMC. DO NOT install ANY callerID programs (Which shows callers face) since they, at least with my phone, messes up system files and crashing starts. Remember to set up text message service number as first thing, after format, because if you try to send MMS without service center number, phone bugs, and you have "sending MMS picture" top of the phone hole time.
This helped me when I haved crashing while writing MMS messages, and hangup's time to time.
And god damn this FW 12 is buggy