D-Link DIR-615 :: Can't Access Internet With Wireless Devices

I recently went into my router and changed my security settings so that my router is WEP protected. I was having issues with somebody feeding off on my connection and causing problems with my Internet provider. I had changed it to be a secured network before but somehow it became unsecured. So, I set up an admin password and such so nobody else should be able to get into my outer . Anyway, after setting it up to with the WEP, now I cannot access the Internet from any other device except my main PC to which the router is connected.I usually get some sort of error stating that there is "limited on no connectivity" when I try to connect my laptop or Archos Home Tablet device. Yet, is reads that the signal strength is excellent and recognizes my network as existing.