Newbie Struggleing with Wireless Security

My home network is working ok. Dell PC on LAN with laptop wireless and a
true mobile 2300 router. I would like to limit wireless access to only my
laptop. I tried by going to "my.router/advanced settings/access control
settings". There is a checkbox for enabling MAC access control and a table
for entering MACs. I did that a while back but unfortunately had the wrong
MAC # for the laptop. So I simply unchecked the enable box. Now that I
think I have figured out the real MAC for the laptap, I want to go back in
and enable MAC access control and edit the erroneous number I entered.
However, the add MAC/edit MAC links are totally unresponsive.I tried
restarting router; did not help. Is this a hardware problem? Any ideas
would ber appreciated.
Thanks,
Don