WLAN connection problems have been observed when connecting with Symbian^3 devices (e.g. Nokia N8-00, C6-01, C7-00, E7-00) to D-link G604T wireless router. The D-Link router doesn't in all situations handle the sequence numbers properly, causing the WLAN connection to fail.
The workaround is to restart D-link G604T access point and reconnect from the mobile device. The WLAN connection works usually correctly if the Symbian^3 device is the first device that connects to the access point.