Slow connection speed using wireless

Got an XPS 8300 with a 1501 Wireless-N  WLAN half-mini card. I'm using a Linksys WRT160n router which can handle up to Draft 802.11n.

When wired directly  to router I'm getting ~21-25Mbps. When I go wireless, it's pitiful - down to ~2-4Mbps. We just got a new laptop in the house (a chromebook actually) and the wireless throughput on that is equal to my wired throughput  (21-25Mbps).

I'm using WEP security on the router.

Can anyone tell me what setting to check/modify to get my connection speed up? Everything I checked seems to be OK and the driver version is up-to-date.

Thanks a million for whatever you can tell me.

Joe