I have an Acer 4730z laptop which has Ralink 802.11n wireless LAN Card and has Windows vista home premium.

I bought this laptop in US and there I used with D-link DI-524 router and had no problems... I also used it while traveling within US at hotels, airports etc and had no problem with wireless connection.

Now the laptop is with my father in India. There he has Pronet PN-108WRT - 108Mbps Wireless Router. Detail specs of this router are here.

Now the connection works fine if he is very near to router. But if he goes to next room it stops working. After some setting changes, he was able to make it work for about a min but then again it disconnected.
After that when he checks available wireless connections, it just shows pronet for few seconds and then it doesn't show.

Of course, first guess can be that wireless chip/signal is not strong but I will be really surprised that it can not penetrate even a single wall.

Now, he also has sony laptop (with Intel(R) Wireless Wi Fi Link 4965 AGN) and that is working perfectly.

My guess is that may be the acer is trying to connect at 802.11n network while router works only on 802.11b/g network. Could that be a problem?

He did update drivers for the Ralink but still did not make any difference.

What other things we can try?