It seems that your DNS is working fine but either the router is not routing or the connection is dropped. I would sugges that you do the followings,
1. connect the pc to the router
2. from start->run->cmd:
type "ping 61.172.201.195", post the results &
type "tracert 61.172.201.195" and post the results.
Is the modem new or somebody has changed the configuration? If it's not new, try to set the configuration back to default and try again. If all doesn't help, connect the pc directly to the modem and repeat what you were told just to confirm that the link is good.
I wont be here for too long. So, if you can post the results here, maybe we will pick it up tomorrow.
Good luck.