Need Help with home network

First let me admit that I am not a network guy and so some of my questions probably seem simple to some of you. Please bear with me and help me out.

I set up a simple home network with a netgear wireless router, a laptop, and a pc. I have two problems.
1) I regularly get “Page Cannot be Displayed” errors in IE. If I open a new browser I can get through but it takes 1-3 tries.
2) I cannot download from p2p filesharing networks like LimeWire. LimeWire says it is being blocked by the firewall and disconnects.

Any suggestions?
Environment
Windows XP SP2
512/128 Internet speed

Thanks,
Xearon