sms icon?

Heyy. I'm new to CrackBerry and BlackBerry alltogether and I have a quick question. I just got my first blackberry last week and it has so far been a great phone. But, occassionally when I send a sms, I am immediately shown a small red box icon with an L shape in the upper right hand corner of the box. I have searched everywhere and am having trouble finding out what this icon means. It comes up next to the message, where the sent or failed icon appears. Any Ideas? ....Thanks

This means your phone is searching for a good enough connection to send the message. Does your message eventually send, or does it just stick on this constantly?