Facebook messages on my blackberry won't delete...?

Ok so I have a blackberry curve and I have facebook on it. I deleted all my messages in my inbox but everytime I go back onto facebook they are there again and then I get the facebook emoticon telling me that I have new facebook notifications so I look for them and it turns out they are just old mesages appearing to be new again. This continuously happens everytime I go onto facebook on my blackberry. Please help as it is rather annoying:)