Thanks to SFAB's explicit advise, I think I've corrected my problem, albeit temporarily. I had the "No blue light, no SIM registration issue." I tried new firmware (.09), confirming 911 settings, turning off the firewall (temporarily as a test), and resetting the cable (Comcast) modem and router, all without success. HOWEVER, with respect the resets, I was not first disconnecting those devices wired and wireless connected to the router. But in reading SFAB's posting, and then the T-Mobile reference on Power Cycling,
http://support.t-mobile.com/knowbase/root/public/tm51789.htm?A2L.SERVICE=T-Mobile_HotSpot_@Home
I came across the instruction to disconnect those devices connected to the router before reconnecting the modem and then router. As it happens, I have two computers and a mobile phone connected via wireless, and a network harddrive connected via ethernet into the router. My previous resets had occurred with those devices turned on and they were attempting to establish connectivity once they saw the router's wireless reappear. So when I turned off my computers, disabled the mobile phone's connection, and disconnected the hardddrive, and then went through the power off / on cycle, I experienced success. First I turned on the modem, waited 30 seconds for that connection to my ISP to become firmly established, and then the powered on the router. The router's blue light came on about 60-90 seconds later and I heard dial tone for the first time in three days. I then reconnected my wireless and wired devices and the blue light remained on. And as it happens, I needed to modify a setting in the router (turn the firewall back on) and that caused the router to reset. Once it reset, I lost the blue light and dial tone. So I went through the same sequence (disconnect all devices from the router and then Power Cycle). Blue light came back on.
In looking at other postings, I suspect there is a bug in the router and all the connectivity attempts occurring at one time is taking priority over establishing the SIM registration. This might be why those who are running the Linksys router BEHIND their existing wireless have success. (ie. there is no other device other than the telephone connected to the Linksys router, so there is no contention when it is booting up.) Also, I suspect those that who were performing port redirects, firewall changes, and confirming 911 settings may have co-incidentally experienced some success, but the fix was probably directly related to the Power Cycle and an unnoticed change in a devices connectivity status, and not the modification of those router or T-Mobile settings directly.
Naturally, I'll wait to see how this goes for a few days. The fact that I had success a couple of time today isn't absolute proof, but repeatable success is promising. From other postings, it looks like I'll have to adopt this Power Cycle process occasionally (in the event of a router reset or some other circumstance.)
Message Edited by Commonboy on 10-03-2008 10:53 AM