Is your ISP MaxNet or T.O.T??
I have MaxNet and they sometimes try to shape the bandwidth I'm using.
I've already complained several times (with some threatening emails), which prompted them to check my line and then it got faster for quite some time. After that it started again till the next mail of mine.
Anothe issue I had so far was some Spyware program I have installed, which slowed down the speed. After I disabled the "on-guard" function, my connection speed got better as well.
