Wifi Problems on RPI

Having problems getting Wifi to work with my usb dongle on RPI
Has worked fine with other Linux versions.
Entering lsusb appears as listed, also iwconfig o.k.(although not connected)
So assume hardware wise o.k.(Realtek chipset)
Have tried various changes in /etc/network/interfaces file but no joy.

Any advice appreciated.

Regards,

Mark. :question: :question: :question:

On network, configure appropriately and hit the second save button. Then wait at least 30 seconds and reboot
let me know

Had problems getting the wifi dongle to work.
Modified /etc/network/interfaces file as shown below.

auto lo
iface lo inet loopback

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp

wireless-essid YOUR SSID NAME
wireless-mode managed
wireless-key YOUR PASSWORD

auto eth0
iface eth0 inet dhcp