Some linksys routers will block bonjour traffic. Check to see if "'filter multicast" is enabled in the router's settings. Or use a better router.
My suggestion is you disable sleep mode as a test and see if that solves your problem. Leave the lid open. Leave your laptop plugged in.sleep mode on laptop? cant do that, dont want it running all the time and esp when the lid is closed.
if you mean sleep mode on something else then im all ears