Reset of Linksys wrt54 g wireless

In short, i have to keep cloning one of my Pc's mac addresses.

Question is why??

First i have comcast.
Second: i have a linksys cable modem.
Third: I have a WRT54G using both wireless and rj45 connections.

Wireless unit is about 3 months old, up until 2 or 3 days ago
everything was fine.

Than it started, could not connect, "FINDING SITE" is all that was
displayed, well a little quick troubleshooting told me that the
wireless router was to blame. After trying ALMOST everything under the
sun, linksys said try cloning one PC's mac address, and that worked.

For about 1 day. The problem has happend again twice, both times
cloning the mac address works.

I have 2 Pc's and a wireless laptop, besides that, nothing has
changed.Nothing that should matter anyways. One thing that has changed
and i will change after this writing is that for added security,
besides data encryption for the laptop, i added each pc's mac address
into the routers configuration and told it to limit connections to only
those Mac addresses.

Maybe i am stupid, but this should not cause the problem im having.I
had it configured this way for 2 weeks before the problems started.Now
every day i have to clone that mac address.

Help