trouble connecting to some wifi access points

[tom arnall <kloro2006@gmail.com>]

I am having trouble connecting to one of the wifi APs in my neighborhood. 
Following is my connection script.

	sudo  iwconfig ath0 essid "linksys"
	sudo  iwconfig ath0 ap 00:18:39:20:29:CA
	sudo  dhclient ath0
	sudo  iwlist ath0 scan 
	sudo  ping xspace.com

Following is the output when I run the script:

	sit0: unknown hardware address type 776
	wifi0: unknown hardware address type 801
	sit0: unknown hardware address type 776
	wifi0: unknown hardware address type 801
	Listening on LPF/ath0/00:0d:88:bb:51:91
	Sending on   LPF/ath0/00:0d:88:bb:51:91
	Sending on   Socket/fallback/fallback-net
	DHCPREQUEST on ath0 to 255.255.255.255 port 67
	DHCPREQUEST on ath0 to 255.255.255.255 port 67
	DHCPDISCOVER on ath0 to 255.255.255.255 port 67 interval 4
	DHCPOFFER from 192.168.1.1
	DHCPREQUEST on ath0 to 255.255.255.255 port 67
	DHCPACK from 192.168.1.1
	bound to 192.168.1.109 -- renewal in 43200 seconds.
	ath0      Scan completed :
         	 Cell 01 - Address: 00:18:39:20:29:CA
                  	  ESSID:"linksys"
                  	  Mode:Master
                  	  Frequency:2.437 GHz (Channel 6)
                  	  Quality=34/94  Signal level=-61 dBm  Noise level=-95 dBm
                  	  Encryption key:off
                  	  Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              	9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s; 36 Mb/s
                              	48 Mb/s; 54 Mb/s
                  	  Extra:bcn_int=100


But when i try to use the seeming connection, there is nothing.

For most of the APs to which I attempt to connect, everything is fine, but in 
a few cases like this one I can't connect.

Thanks very much in advance,

tom arnall
north spit, ca
usa