I just wanted to add another post for the lock-up issue. All I can hope is that if Linksys sees 10 posts a day they'll maybe look into the problem and provide a solution.
Setup is a notebook with a Intel PRO/Wireless card and a WRT54G, v2.0. Sometime after upgrading the router firmware to the latest 4.21.1 the problems started (wish I had written down the old firmware number). On occasions when powering up the notebook it finds the network but it will not connect. I have the process of hard resetting the WRT54G and restoring the configuration file for it down to a fine science.
Thanks to the following members for the most promising posts. I'll give them a try and see how it goes.
"I'm also hoping you can "fix the router" and here is a clue as to what should be worked on. Check out this link: http://www.intel.com/support/wireless/wlan/sb/cs-006205.htm and note the cause. Power Save Polling not handled correctly by the router manufacturer. My 54GX4 worked well for a year until I brought home my new laptop with a 3945ABG card in it as rmeyers has and much trouble ensued. I did the recommended short term fixes from Intel and I'm up and working, typing this wirelessly without trouble. I am however going to see increased power consumption as a result of the changes. I'd like Linksys to correct the handling of PSP so that I can change back to the original settings. I did not see anything on the version info for the latest firmware addressing this."
"For those who have had wireless only issues w/ this router, I found a solution that worked for me. Hopefully, it will help somebody else. It's the "Network Density" setting under the "Wireless"->"Advanced Wireless" tab. The default setting is "low" so I moved it to "medium" and all of sudden, everything seemed to work better. My packet loss/speed went from 25% loss/200ms to 2% loss/4ms. This setting apparently increases the transmitting power of the wireless signal. After somehow noticing that the number of Wireless SSIDs I see in my area grew by 3x-4x in the last few months, I decided to give this a try."