Isn't the Open Signed root certificate missing on Nokia 5800 (S60 5th) ?
I am trying to install Open Signed application on my 5800.
The device refuses the certificate due to date/time reason.
If the phone date/time is correct or set in the future (2008/11/29) or set in the far future (2012/10/28), we get “certificate expired” error at the installation.
If the phone date/time is set before 2008/10/28, we get “Certificate may be not valid, is expired or phone’s date settings may be incorrect”.
If the certificate does not contain the device IMEI, the result is the same.
BUT if I try to install a previously Symbian Certified Signed version it installs and works fine.