It seems I was a little too hasty in giving Firefox 3 Beta 5 as much credit as I did earlier. Ffb5 does work extremely well, untill it doesn’t. As far as I am able to tell, the browser becomes extremely slow at random times often after keeping the browser open for some time, this is a result of a boost in memory usage and cpu load for no apparent reason. Surprisingly this problem does not occur to everyone, I only found a few reports. Nevertheless, this is a very big issue, that didn’t occur in ffb4. Obviously the browser is in beta stage, so whining is out of question. However, I could have recommended ffb4 to those willing to experience the speed improvement with only a few downsides, but I can’t say the same for ffb5. As the release of Firefox 3 draws nearer, I hope this problem gets fixed as soon as possible. I will still keep using ffb5 
Post comments if you are having a similar problem and also if you know what’s causing it.
Firefox 3 Beta 5 Not So Resource Friendly Sometimes
Published April 23, 2008 UncategorizedTags: 3, 4, 5, 7, best, beta, browser, bug, crash, date, explorer, fast, fastest, ff, ffb5, Firefox, freeze, fx, gran, html, ie, internet, issue, javascript, Linux, memory, mozilla, nothing, opera, paradiso, performance, personal, problem, ram, release, rendering, secure, slow, speed, ubuntu
I have the same problem too on Ubuntu, its kinda strange, i hope it will be fixed in the next release, and i hope the next release is not too far, because it really is horrible.
Having the exact same problem. Not sure why. I installed the cpu graph under Ubuntu and sometimes it crunches the CPU horribly when slow, other times, it has no CPU usage and is still randomly slow.
hello,
using a ubuntu 8.04 machine on a laptop and FF3b5, i have the same problem.
as i use the built-in gnome systen monitor (which sits in my panel as an animation), i could see that the CPU is loaded by “IOWait” instructions.
i have no idea what causes it; i refuse this being caused by some addon.
i hope it will get fixed soon.