I have an error starting message : CLASS NET.RIM.DEVICE.API.SYSTEM.WLNAINFO NOT FOUND

You need to upgrade your firmware to 4.5. to avoid this error.
The upgrade of the firmware for the BlackBerry is free of charge.
Please connect your BlackBerry device with your PC and open this URL.
http://na.blackberry.com/eng/update/
It will check for the new firmware and let your upgrade your device.