Prevent express card from disconnecting

Earlier this year I purchased a Cisco/Linksys Wireless Express Card to replace the internal Airport Card as it was no longer receiving signal properly (think Apple Techs damaged antenna during screen replacement). The card works great - much better than the internal Airport. However, unlike the internal card, whenever my laptop activates the screen saver or goes to sleep, the express card disconnects from the network. How do I prevent this disconnection?

Thanks.