Belikin wireless network card

I have just installed a wireless network card after previously using a USB
wireless plug-in device. It connects successfully and has maximum signal
strength, but the signal keeps dropping out after 30 - 60 seconds and then
has to re-connect. It works perfectly during the period when it is
connected. There are no software / firmware updates available for the card.

I have now gone back to the USB device, as the card was too frustrating.
Does anyone have any ideas what is causing this? My laptop works perfectly
off the same router.

Many thanks, Mark