Find out which version of the router it is (look on the label for the version "v") and then log onto your router to find out the firmware version.
Check the netgear site for a firmware update as I have the same router and had the same problems. I went so far as to buy a bigger antenna but that didn't make much difference.
One of the firmware updates has "Improved wireless stability". I installed the latest firmware and I now get a full, uninterupted signal throughout the flat.