Problem with ports on Mac, but ports are fine with Vista?!

Hello all,
I am new to Macs, I have a Macbook pro, running os x 10.6. and unfortunately, my p.o.s. Vista netbook is outperforming it! I appeal to your love of Macs to help me on this one.

My problem is that I am able to download a torrent fine with my Vista netbook (and before anyone freaks out, i am using it to download Openoffice on my mac, and occasionally other legitimate torrents, not piracy. In fact, I rarely ever use torrents, but the sheer frustration that my slick new MacBook can't do what my crappy Vista comp. can do is driving me nuts!), using the same connection as my Mac, but when I use any of the torrent clients (Vuze, Transmission) on my Mac, they all say that my port is closed and the d.l. lags at like 2.4kbs, while on my Vista laptop, I get the greenlight saying the ports are open, and everything is fine, up to 300kbs.

I have searched but really can't seem to find an answer that doesn't involved screwing with the router. But, if I can download on the same connection, with the same modem (siemens gigaset se 261) and router (tp link 941nd) with my Vista, why can't my Mac do the same? I also notice this is a problem when trying to set up things like Remote Desktop. Please, any advice or help would be greatly appreciated, and thanks in advance!

Do you have the Mac firewall on? Do you have any programs like little snitch running?

You usually don't need to open ports on your router to get torrents to work.

Also if it is new - download a bunch of stuff. For some reason some Macs start off slow downloading then get the full bandwidth. I know my MBP took a week to get full bandwidth downloads - I have no idea why.

Yeah, I've allowed the programs in my firewall, also, tried turning firewall off, but no change. All the port checking programs say i'm closed, yet again, my Vista is open and has no problems. And I hear you about not needing the ports open, but still my dl's will start fine, slowly get going, then peak out, and eventually drop down to about 2.4kbs while my Vista keeps chugging at the right (high) speeds until it's finished.

Also, by "new" I mean, I've owned it for 6 months. But at one point, I was able to download fine, then sometime later, i was not, and it's been this way for a about 5 months (i've been trying many other things before finally posting). I even tried to reformat the computer thinking maybe I had goofed with a setting trying to fix he problem, but no, still nothing. Thanks for the advice though.

Any other thoughts as to why my Vista netbook can do what my MBP cannot?