I am computer challenged so have very limited knowledge about "programming" but here is my problem. I just bought a N900 which connects to internet through Wifi very intermittently. It connects through ATT GPRS flawlessly but not through Wifi.

I have tried it both at my home and corporate wireless network.

(My other N900- another story, returned because it was bought at higher price) connected to Wifi flawlessly but this other unit connects only intermittently and most of the time gives page error. I read somewhere it might be a dns auto-retrieve error. Can someone teach me how to flush the dns cache (step by step for a layman) or what could otherwise be the problem and how to troubleshoot or should i just return this one too?

Well power cycling my wireless router and N900 both seemed to have helped.

You want to have a look at this thread about the Wifi issue http://talk.maemo.org/showthread.php?t=35600

You need to make some changes to the power saving mode (it's a known bug and is being fixed for firmware update)