Im experiencing similar problem earlier on. I send a message to my friend 14 hours ago and didn't receive any reply. I messaged another friend and he replied. My female friend told me she replied my message and asked why I didn't reply her. I'm using 15092012-1835 version. I uninstalled and deleted the .db but it didn't solve the problem. I can see her type, but her messages would not appear, but she can see mine. I revert back to the 14092012 version and it is working again.