Linksys boxes freeze up occasionally (once every few months) and have to be power-cycled. Suspect this is happening if your outside Web access suddenly stops working; ping the Linksys box to check.
These catatonic episodes may be related to dirty power; at least, they seems to happen more frequently in association with electrical storms and brownouts. If you think this has happened, just pull the power connector out of the back and plug it back in. The Linksys should reboot itself within 30 seconds or so.
There is a more severe failure mode that I've only seen once; it's more like an epileptic seizure than catatonia, and involves strange blink patterns on the Link, Collision, and 100Mbit diagnostic lights (the 100Mbit light should not normally ever blink).
If this happens, power-cycling the Linksys won't suffice; you'll have to hard-reset the thing. Some versions (like the BEFSR41) have a reset pin that you poke with a paperclip end through a small hole in the front panel labeled Reset. Some versions (like the BEFW11S4 and WRT54G) have a reset button on the back. You have to hold these down for about thirty seconds to hard-reset the nonvolatile RAM. This will lose your configuration settings.
Linksys blue boxes have a webserver embedded in their firmware. The normal way to administer one is to point a browser at its IP address on your network. You program the box by filling out HTML forms.
This is a nice bit of design that neatly avoids having OS-specific client software. But some older versions of the webserver firmware have a quirk that interacts with a bug in Mozilla (at least at release 1.0.1) to make the interface almost unusable. Fortunately, the recovery procedure is trivial. This bug was known to be present as late as 1.40, and also interfered with Netscape; it is absent in 1.44 and a good reason to upgrade. We have a report that Mozilla 1.3 fails with 1.43, so whatever change fixed the problem likely came in with 1.44.
The symptom you're likely to see is a broken-image icon at the upper left hand corner of each page. The broken image is a series of file-folder tabs for an image map. That image map is how you get to the other web pages.
You can recover by right-clicking on the broken-image icon. Select "View Image", then back out. This will build the image map correctly.
You will almost always have to do this on the first page, but it often won't trigger on later page loads.
Here's what's going on. Mozilla tries to stream multiple concurrent requests at the webservers it talks to in order to speed up page loading. The dimwitted little firmware webserver in the Linksys is only single-threaded and doesn't handle concurrent requests. So there's a race condition. When you hit the window just right, you get an aborted request and a broken graphic.
Most other browsers are immune to this problem. Konqueror doesn't trigger it. Neither does Internet Explorer.