I just purchased the Samsung Galaxy S2 last week. Over the last week people have mentioned that I haven't been replying to their texts, however, I never receive them! One person is on AT&T, the other is on Sprint. Both have iPhones.
When I look at my online data usage, it shows that the person texted me and that I received it....but it does not go to my phone physically. I've restarted the phone and they still do not show up.
This happens randomly. I'll text a person 100 times and maybe 1/100 times their text will not reach my phone.