Try to avoid the usage of special characters for WEP-encrypted networks, some access points have their own way of working / methodology. If you however want to use those characters then kindly enter the WEP-key on the Network Player in hexadecimal form.
Some older access points may have issues with the option SHARED NETWORK AUTHENTICATION. Try to use other options provided by the access point.
The Network players do fulfill the requirements of the WiFi-alliance and as such connection to most available routers should be given / possible. In general PHILIPS recommends to use WPA-PSK encryption as this is providing a more protected / secure network and also it allows an easier entry of the security key / credentials.