N type wireless access point – poor connection

Having substituted a G for with an N AP, I’m disappointed to find I can’t get a reliable connection at 50m. I could, just, with the G kit. If I set up the remote computer with a manual IP it does connect but a ping loses most of the packets, in spite of the signal being reported as “strong”. I can’t use a wireless range extender since I haven’t seen any using N.

Any ideas?