MAC address filtering on, yet new WiFi card could connect

Hi,
Interesting problem of some concern, I received a replacement SMC 2435W
wifi pc card to replace a defective one. I inserted the new card into the
laptop and got instant connection to the router (192.168.2.1) and to the
Internet. Yet I later noticed I hadn't updated the MAC address table with the
MAC address of the new card (it's different from the MAC address of the old
card). Yet the new card connected no problem.

I also noticed that although I have "broadcast SSID" disabled, the
software for the pc card shows my MN-500 router's SSID (others have posted
that the SSID is broadcast anyways, so my wifi network isn't at all invisible
to others as I thought).

I'm a little concerned that I may not have my security settings correct. In
summary, I have WEP enabled, with 64 bit word, and have two entries in the
MAC address table (my pc Card and my PDA). I have "enable Association
control" checked and "deny" unspecified MAC addreses to associate. Yet it
seemed the new pc card was able to associate without my updating my MAC list.
Any hints on what I may have missed.

-Tony