Nokia x6 not receiving text messages?

i had my nokia in july this year. everythings been fine till last week. latley my phone, whether its on silent or general it doesnt tell me when i have a text message. it doesnt make a noise or vibrate only the blink light flashs. i have to regularly go onto menu, messages, inbox every time to see if i have a text message. which is a pain in the ass. i'd be greatful is anyone could help me?