Hi again.
Still hoping for further details about this. Have updated BIOS from support site (couldn't find a more up to date wireless card driver) but connection to internet sites still lost regularly, even though wireless still connected. Message 'Waiting for (site)' appears at menu bar, but connection to site is never achieved. A full Restart always solves the problem, though (but not disabling/re-enabling wireless).
Further help appreciated please.