Next time that happens:

First reset the modem.

Then turn the connection off and on in the control panel.

Disable any firewall software.

Check to see if you're using a proxy in your browser. If you are, disable it. Should be in advanced settings.

Command prompt:

ping google.com

(if the response to that is the operation timed out or no packets were delivered/recieved then enter:)

netsh int r r resetlog.txt

(if that worked, it should just go to the next line)

Then reset the system.

Here's (http://community.livejournal.com/entanglement_rp/31498.html) an OP with her and the worms if you want.