If you work for a business that provided you with your Curve, it is entirely possible that, before providing you with your phone they disabled some of the media functions on it. If it was your business that disabled these features, you would have to speak to the person in charge of providing employees with phones in order to clarify exactly why these features have been disabled (many companies do it to prevent ‘inappropriate’ use of company time and money). If it isn’t a business phone, and you purchased it under your own name from a service provider, you should take it into the store and ask that they remove any restrictions that may have accidentally been placed on the phone without your consent.

So when you press the right side key it displays that message? Who is your provider?

Try to take out the battery while the phone is still on and try it again when it reboots