That model is pretty old, it's probably just breaking down. I checked to see if DD-WRT firmware was available, but it's not.
I mention DD-WRT because it's 3rd party firmware that is more stable than the stock Linksys firmware, and it enables a lot of extra features, one of which is the ability to boost wireless signal strength. I've been running it on my Linksys WRT54GS for a couple of years now, and it's been far more stable than when it was running the stock firmware.
Linksys isn't the only router brand supported, there are many more. I would advise that, while router shopping, you go to:
Router Database | www.dd-wrt.com
Enter the actual model number of any routers you're interested in, and if it's in the database, it will typically show you whether it's supported or not, with a link to the page for the download. They also have instructions on how to flash the firmware. If you have any trouble with finding the model on that page, go to this one:
Supported Devices - DD-WRT Wiki
You can manually look up the make and model there, and each mode;'s specs will tell you what builds you can run. Example, my router can only run the Micro build, because it has very little memory, but other routers can run larger versions. I would also recommend Newegg, they almost always have the best prices on computer stuff, and everyone raves about their customer service. Some of the routers now even say DD-WRT support in their descriptions, which should tell you how prevalent DD-WRT firmware has become.