When I first upgraded to Mountain Lion, Messages worked flawlessly. I had my friends start texting me to my email address instead of phone number, and I was able to freely converse using my phone or Mac; messages were perfectly sync'd between my devices. Every single message sent to my phone also went to my Mac, and vice versa. I've noticed that now, messages are "missing". Often, I will have a conversation on my phone, come to my Mac, and many of the messages do not sync. So, I can't continue the conversation there. This problem is rendering Messages virtually useless for me. If I can't guarantee that I am receiving messages, then I can't use it. Nothing has changed in my configuration. This became frequent around the time of the iPhone 5 release, so I wonder if Apple's iMessage servers are overloaded. Prior to this, Messages would sync everything, although frequently, the messages would appear in the wrong order. I have searched in case Messages is just putting the missing messages sometime in the past, but no, they just do not exist. I have all three of my email addresses and phone number configured to receive iMessages. I only really chat with two people, and they both have theirs configured properly as well. This isn't a case of someone texting the wrong address or something. Apple's servers, or the Messages for Mac software, just isn't syncing properly. Anyone else having this problem?