I think I may have found the problem and it's not (at least at this point) Forecastfox...
Typically I'll have 2-3 separate instances of F/F running each with multiple tabs.
This last week I've limited myself to one instance with more tabs...CPU has remained 'calm' so far...haven't watched memory as I have 2gb and was never close to running out.

This thread was timely as I had noticed that FF was using up usually 120mb and up to 160mb of memory (no CPU issues for me). Now I understand when I open many tabs, but when I close them the memory usage doesn't drop.

So I uninstalled unused extensions and disabled ForecasFox but this didn't seem to help.

Then I found this which did the trick - http://www.freerepublic.com/focus/f-.../1327586/posts

I don't believe anything he said after reading that.

BTW, I'm not having any cpu utilization problems with FF2.x. But I don't run things like forecastfox or anything else that does anything in the background that could increase cpu utilitzation when I don't need it. I have Fasterfox, fireftp, flashblock, flashgot and linkification installed. (in addition to talkbalk and Dom Inspector.) I don't enable the cache-ahead features in fasterfox.

There's probably a memory leak in 2.x. I'm sure it will be plugged eventually. If you want to reclaim the leaked memory, you have to completely restart ff. If you have enough memory in your system, it probably doesn't matter. If you run taskmgr and look at the performance pane, if your peak commit charge is greater than the amount of physical memory you have installed, then you could benefit from more memory, or perhaps by restarting ff.

-David

I have the same problem with Netscape 8.1.2, and it apparently runs a program called "updatelists.exe", which also comes online and takes up almost 100% CPU time - anyone can confirm this?

Well, after watching things for a few more days I am finding that the memory usage still creeps up like everyone else has reported, but the CPU usage is still behaving itself without the forecast fox. I haven't really had any time to do much more since I posted. I can live with fairly high memory usage until I can take the time to tweak much easier than I can live with high CPU utilization. Gotta admit, somehow this whole experience leaves me just a little bit disappointed with Firefox. Guess I'll just have to try to be patient and wait for an incremental fix to the slow memory leak....I'm not going back to IE!!!

If you really want to, you could find the bug in bugzilla and add yourself to the cc-list. I'm sure they will plug some of the memory leaks eventually.

-David

Google Toolbar??
 

Just after reading this, a friend asked me to look at some funny behavior on his machine (Thinkpad T-series, I beleive)

I don't think it was related to the actual problem, but I also noticed that his CPU usage was unusually high. Checked and it was only when FF was running, but he wasn't running nay of the suspected add-ons.

The only thing there was google toolbar. I removed it and the CPU usage was down. Downloaded it again from google and reinstalled and no bump in usage.

It may have been because I chose not to enable page ranking and I have no idea if he had it enabled before, or it may have been a new revision of the toolbar software, but maybe that'll be a clue for someone else.

Didn't the google toolbar have a folding@home option at one time? I seem to recall that it did, but I don't know if you had to download a special version to get the f@h stuff included or not, and I'm not sure if it still exists or not.

http://en.wikipedia.org/wiki/Google_Toolbar

According to the wikipedia article, Google Compute (the f@h tie-in) ended in 2005.

-David

Another interesting read:

http://kb.mozillazine.org/Memory_Leak

It seems the problem of memory usage and CPU usage is at least partially caused by ForecastFox. Of course, Firefox and ForecastFox are blaming each other for the problem.

Now, with the release of 2.0.0.2 of Firefox and 0.9.5.2 of ForecastFox, the CPU problem seems to be gone. It may take a few days of usage before I notice any different regarding the memory issue, but now, my Firefox hardly registers in CPU utilisation...