After finishing my work at the campus, i went back to my house and i saw my modem's LED turned to RED, meaning there was a problem. So i turned off my computer and waited until the connection has been restored. At around 4 PM, i went back to campus to teach my class again and when i arrived at home at around 7 PM, i turned on my modem and voila.... i can connect to my Speedy again
The strange thing is that when i was in the campus, i can browse using the same ISP (Telkom), but with different name, AstiNet (which i thought for corporate users). I thought they share the same system, but unfortunately, i was wrong.