funny airport signal behaviour .. culprit: security update -004?

[edgarbc1]

Intel imac, airport extreme card inside...
airport extreme base station..

i was used to having all 4 bars full signal strength

but lately im getting less.. 2 and even cuts out to 0 bars..
and i find that it "looses" the name of the airport
base station ( i dont broadcast the signal to everyone, you
have to know the name of the base station and password -
closed network)

and the only thing i can attribute this to is the security update
004 which was released all that not long ago.....

have you heard or experienced similar?
EBC