Slow Wireless DSL connection

I have DSL at my house and my connection is normally pretty fast. I
just set up a wireless network. My computer says it's connecting to
the network at 11 Mbps (Excellent Signal Strength), and I can surf the
web fine. However, while I download files through a peer-to-peer
service like Kazaa, even if I'm transfering only 10-15k/sec through
Kazaa, my internet connection slows down to almost nothing. Web pages
that would normally load in a second or two, take more like a minute.

Is there anything I can do about this? Is the problem with the
connection itself, the wireless hub setup, my computer, or something
else?

Thanks in advance for any help!!