This could be due to a hardware failure but but Curve 9320 users can try the following loading a new firmware - which has worked for others).
Go to https://swdownloads.blackberry.com/Downloads/entry.do?code=B1A59B315FC9A3002CE38BBE070EC3F5
1. Select Blackberry Curve 9320 - click Next
2. Choose any of those firmware bumdles by clicking on 'Download'...
3. Complete the form there and click Next (not an important stage but it must be done)
4. Select the 'Agree' radio button and click Next
5. Click on the download button and the firmware file should start downloading
6. Now navigate to your Downloads foldee and double click to instal the .exe firmware file.
7. Navigate to Local dirve C.> Program Files > Common Files > Research in motion > App Loader > ...delete the file called 'Vendor' in there
7. Now double-click the App loader file with a cellphone icon to launche the App Loader