Go to mobile phone Nokia 5800, and go to the application Manager. Open function, and run the setup, software installations, set the value "All" and to check the certificates will use the property "Disabled". This is true in cases where the device gives an error associated with an unsupported app or just a bug in the certificate.
If you have a mobile device Nokia 5800, the message "Certificate expired" and the application does not require signatures (updated certificate), go to menu settings date and time, change the value of six months ago. Install the program on your phone again, removing it if it still remains, then set the correct date and time.
If you encounter problems with installing programs with the extension *.sis install version intended for operating system Symbian 9.1. If it is in your case, the menu of the application Manager repeat the steps described in the first paragraph to disable certificates. If that doesn't help, put the date and time on a year ago. This also applies when there is a message about an unsupported application, the error in the certificate or damage in the installation file.
To resolve problems with certificates, use the easiest solution is to reset your mobile phone Nokia 5800 to factory settings. This is not done from the mobile phone menu, and in standby mode using the enter combination *#7370#. Unlock code then will be 12345.
Please note that this action will delete all files, contacts and other custom items from your mobile device, so it is best to pre make a copy of computer data with the paired device in the synchronization mode.