WHY DOES THE BLACKBERRY ICON DISAPPEAR?

[Alexandra Kaz]

So, last night and today, the BlackBerry symbol keeps disappearing, this is the icon in the top right corner and as soon as I switch my phone off and on again, it reappears, but after a tiny short while, it disappears. So then I can't access Twitter or BBM, or the internet or BlackBerry App World. I tried taking battery out and then put it in, but this still happens. Why does this problem occur?
Thanks

[Joe]

thats normally just a poor network connection. it happens now and then on the blackberry i have.