Why has BBM stopped working?

Okay, so I have a Blackberry Curve 9360. Usually my BBM is fine, completely fine. I went to school, and obviously my phone was turned off as I do every day. When I got out of school, I turned on my phone and waited for my BBM to refresh. But it wouldn't, no new status's or messages would come through. I tried sending messages to about 5 of my contacts, but it didn't even send and just came up with a Red Cross. I know for one, that none of those contacts would of deleted me or deleted their BBMs. I tried turning my phone on and off, rebooting my phone about 3 times and turning off wifi&3G and turning it on again but nothing has seemed to work. I'm on a contract so my BBM can't of run out or anything, I'm really confused and need help ASAP x

Assuming you tried the good old style Battery Pull reboot, not simply on the power button...

Check your connectivity status - network should show as 3G (upper case) and a BlackBerry logo near the signal strength bars. If that looks OK test your data functionality by sending an short "test" email from the phone TO your own email. If everything works the phone will receive the test mail which proves your BlackBerry data is working. You could also try adding your own PIN as a BBM contact and talking to yourself (sounds odd but it works).

If no BlackBerry data works you need to contact your cellular provider.

If BB data is working for email but not for BBM there are three causes to check first -
Your cellular provider is having a technical problem which will probably get fixed within a few hours
Your cellular provider is blocking BBM (more likely in Middle East areas, less likely in Europe and N America)
Your BBM software is corrupted.

Hope this helps