Finally my Internet connection is back today. The technician came back and bring me a new modem, since my old modem was the root of the problem. My old modem was Shiro and the new one is JKNetworks. The technician told me that Shiro is a bad product, but IMHO, it's more configurable than JK. You can have more feature in it, rather than the simple version found on JKNetworks.
I have no experience with JKNetworks, so any Speedy users with JKNetworks are willing to share their experiences with it?
Oh yeah, i have to pay 220000 IDR for that modem, since the warranty for Shiro was only three months and i have been using Speedy since January.