It could be that you are on a cable modem like everyone else on your block (or in your apartement) and when everyone gets on at the same time (around nighttime), your connection is slower due to the fact that you all share the same cable line and that could cause issues.
Maybe you need to switch to a DSL provider and see if that fixes the problem....
I've been having a problem with my cable internet from comcast for months, probably over a year, and nobody there seems to be able to help.
The biggest hurdle is that the issues happen over night so it seems like they can't really do anything as they won't send a tech out at that time of night to see the problem.
The problem is that starting sometime between 10-12 at night and going until the next morning, my internet freezes up every few minutes. Sometimes the freeze lasts a second, sometimes a minute, sometimes it goes out completely. I can hardly play online games on the PC anymore as it's constantly freezing me and my Xbox is now completely useless as the freezes totally DCs me from Xbox Live every few minutes.
During all these problems my modem never seems to go out. All lights stay on as normal. And when I call the tech line and they check my modem they ALWAYS say my modem looks good, even when it's going haywire on my end. The ONLY time anybody ever saw anything was when it did it ONCE during the day while a tech was here. He said it was bit rate errors. But nobody has ever seen a problem since then, even though it still doesn't work right.
I've bypassed the router and went straight from modem to PC and the problem still exists.
I'm just about at the end of my rope with dealing with this and could use some advice on something to try if anybody has any suggestions.