distance to the router (within reasone will not affect the connection), and it could be many things.
Check the IP of your desktp and laptop, if they happen to be the same the conflict would likely go to the wired connection, and the conflict is not always reported to the user.
Go to your network places, and select view network connections, and highlight your local area connection (if it exists) or any other icon which appears there to find your IP.
Also if you can access the router from the wired computer, check to be sure that there is no encryption or WEP key, if there is either, you laptop will need to have the same settings on your card.
*Have you recently installed any new software on either computer, or updated the firmware when this happened? Sometimes updating firmware resets WEP keys and your laptop would be supplying the wrong information.