The saga began over a month ago – seemed to take an interminable amount of time to load pages into a foreground tab. Also got lots of “server not found” error messages. Then came the Anti-Virus subscription expiration and new software, and "it seemed to run slower". issues. This was happening on both desktops (mine and my wife's). Thinking something was wrong with the computer, I started there, because they were Celeron 2.4 GHZ machines, and had not been cleaned up for some time. Actually, our 1.7 GHZ ThinkPads (Pentium M) were running faster! General cleaning – dust out, check cables, run diagnostics, etc.
Corrected an error in mismatched memory and installed new NICs (onboard NICs were ranked as abysmal!) Nothing in hardware was going to solve the problem. Actually found that one of the replacement cards was at least 300 times faster than what was onboard!
After getting started on the software cleanup, remembered that just last year, I had replaced my hard drive (second time) using "Maxblast" to move the HD over, there was a full reinstall after that, because it was not acting right (yes, everything was reinstalled), so it couldn't need a Windows reinstall again (well, with Windows anything is possible). However on my wife's machine, there had not been a cleanup for over two years since a malware attack chewed throw her machine.
Registry cleaning with
Another point – both our machines have been upgraded from Netscape (Windows and OS/2) to Mozilla 0.x (zero) to Mozilla 1 then 2 and now 3, bringing over profiles and settings each step of the way. In fact, some of the entries in "about:config" were from when the profile covered both mail (now Thunderbird) and web browsing, so there was lots of junk to clear out.
Had found a work around that involved a batch file to change the priority at which FireFor runs, but did not think that was the right answer (although it kinda/sorta worked).
FINALLY my search for "Firefox 3 high CPU use" led to the blog of GMG (Green Mountain Geek). He had actually seen all those posts from people who were mad as hornets about the poor performance of FF 3. On top of that he was encountering some of the same problems and could duplicate them. His answer was to change a parameter in "about:config". Seems that his testing indicated a problem with memory cache.
A light bulb went off in my brain! Celeron processors do not have a lot of cache, and what was happening was that FF was trying to stuff bytes in someplace that does not exist. On a full Pentium you have much more cache, which could easily account for why the ThinkPads did not exhibit the same problem.
Made the change, and it was like a miracle! BAM! There was the web page without the 30 to 240 second wait.
Thank you to Kirk at GMG for finally finding the answer, and for posting it to his blog.