I updated the router to the latest firmware and went through the steps advised, using the backup/restore function to make the job easier. On testing, the symptoms were just the same.
I then compared my settings with default ones and tried changing a couple of things: disabled wireless security (bad idea but just to see if any change), disabled DMZ, changed wireless security from SPA2 Personal to WEP, changed operating mode from gateway to router. None of these helped. I have now restored the configuration again. I am using PPPoE login type as this is required by my internet provider.
What would I gain by using DD-WRT firmware?
From what I see on other posts, other users have the same router and do not report the same problems which just makes it all the more frustrating.
Any tips welcome.