I've had this issue with Sprint for years. I constantly have issues with receiving messages from a Verizon user. It does not seem to matter what phone I had. I first noticed the issue with an LG Rumor. That phone went swimming, so I then got a Rumor 2. I still had messages that never made it to me. I started to think maybe I didn't have nice friends! After talking with several of the friends I had texted, I was alerted they indeed responded to the texts they received. They too missed some texts that I had sent. I did notice that Sprint phones missed more texts than the Verizon phones. Eventually, I upgraded to a smart phone and got the Palm Pre. I was hoping that this would end the text issue. Unfortuntely, it did not. Currently, I have the Evo and it too misses texts from my Verizon friends. I have called Sprint before but they fained ignorance and said it was an issue on Verizon's end. I'm quite sure that Verizon would insist on the very same response about Sprint. I have been dealing with this issue for at least 4 years now. I have a hard time believing that it is a hardware issue. Especially having the same issue with four different phones.