Speeds alot slower than they should be

I upgraded my internet speed on friday (from 768kbit/256kbit to 4mbit/512kbit). Most of the time the download speed is ofcourse higher than it was but the difference is minimal. With my old connection i got max speed most of the time, while i get around 150 max with the new one (sometimes the speed is terrible, max 50kb/s, even though im connected to alot of peers/seeds). The upload speed is crap often aswell.

I've tried:

everything listed in the sticky (DLed the example torrents too, once the speed was around 300, the 2nd time the download didn't even start, the 3rd time it was max 240 but was slowly dropping to around 150)

Info:

Have a port forwarded, using DMZ aswell

The light is green most of the time (allthough it's usually yellow at first when i start utorrent, but turns green a few mins later), but it can also vary -> switch between green/yellow

im using windows xp,

using nod 32 and sygate firewall (have utorrent on exceptions list),

modem - Thomson TCM420, router - Planet XRT-401c, connection - cable,

the speed tests showed these results -> around 2mbit/460kbit (which puzzles me, since im supposed to have 4mbit/512kbit),

ISP - arnes, slovenia

When you test your connection speed, don't use the internet for any other reason. That means that if you have any other computer on your network, they should probably be turned off, disconnected, or at the very least, not using the connection either. And make sure you selected the test mirror closest to your location/country.