The fact that you get a good wireless signal indicator, and that the connection worked for a while when you first used the Netbook, allied to the fact that you experience the same difficulty when you connect the machine to the router by cable gives a clue - the problem possibly lies with the router.
If you feel comfortable looking at the router settings (which you do by typing an IP address into your browser) you might try deleting all other machines from the address table, then delete the Netbook. Restart the router and the Netbook, and let the router assign a new IP address. See if that makes a difference. If it does, you can add back your phone and any other machines one by one.
If you're not sure how to handle the router settings, post back here with the name and model, and one of us will step you through the process.