SMS issue

[rcb07]

Hi, I am using the newest MIUI (1.5.20) and I have this really annoying issue. My phone is a Samsung Galaxy S I9000 (Global version).
Whenever I send a message, the phone detects it as a foreign message and it plays the message tone and the notification pops up. When other person actually sends me a text my phone detects it as a message sent by me and doesn't do anything.

PD: I had this issue since MIUI 1.5.x if that helps...
I need help please!
Here's an image for you to a better understanding of the issue:

 

[Atermoon]

The "Received" text next to the sent message is the delivery report. That's why it also "beeps" when you send a message.