I am also in Hong Kong and also connected via netvigator. I use the router mainly as wired router, seldom wireless. When I connect my PC (Xp) directly to the the ADSL modem (Arescom NetDSL800) I have no problems surfing.
Now it comes, when I connect the PC via the WHR-G300N my D/L speed gets often MUCH higher. But from time to time the speed will go down to zero, or near zero for all HTTP connections. For some reasons email pop3 mailbox checking still works, slower though. This slowness will last for a few Minutes, then go back to normal speed.