>>Incorrect lease times and/or leases that do not automatically renew are some of the classic problems that some buggy firmware versions have with certain Linksys routers. There are some sites that discuss these problems in nauseating detail; one decent FAQ that talks about some Linksys models is http://www.dslreports.com/faq/linksys
>>
>>If you have an older Linksys router and you suspect firmware problems (or that the device might be unreliable/failing) just go out and get the WRT54GL router I described earlier and put dd-WRT on it. The only regret you'll have is that you didn't do it earlier.
>
>The one I have is the WRT54GS. Is there anything I can do with this one?

You can install dd-WRT on it: http://dd-wrt.com/wiki/index.php/Linksys_WRT54G/GL/GS/GX#WRT54GS

Hopefully it is v4 or below, otherwise it may not be worth upgrading the firmware. This is a case where older is better :)

If you do update the firmware to dd-WRT, record any custom settings you've made in the Linksys firmware because you'll have to re-enter them in the dd-WRT firmware. Recording screen shots is a good way to do this.