New Message - No red icon, or flashing LED

Hi, got my BIS set up properly today. However, whenever I receive an email to my Gmail account on my BlackBerry 8520 - I hear the alert tone, but there is no red icon next to the mail icon, nor does the LED flash red. Also, when I click into the message, it always has a 'tick' next to it, as if I've already opened the message.

Anyone know why?

Thanks.